European Polymer Journal (v.45, #7)
Novel interpenetrating smart polymer networks grafted onto polypropylene by gamma radiation for loading and delivery of vancomycin
by Franklin Muñoz-Muñoz; Juan-Carlos Ruiz; Carmen Alvarez-Lorenzo; Angel Concheiro; Emilio Bucio (pp. 1859-1867).
Gamma radiation was used in every step of the synthesis of a sequential interpenetrating polymer network made of two “smart” polymers: poly(acrylic acid) (PAAc) and poly ( N-isopropylacrylamide) (PNIPAAm), the latter grafted onto polypropylene (PP) films (PP-g-PNIPAAm) with the aim of developing medicated coatings for medical devices. Three steps were followed for obtaining net-PP-g-PNIPAAm- inter- net-PAAc: graft copolymerization of PNIPAAm onto PP films by gamma pre-irradiation oxidative method, cross-linking of PP-g-PNIPAAm by gamma irradiation in water to form the first network, with or without N, N′-methylenebis(acrylamide) (MBAAm), and finally the formation of the second network through the polymerization and cross-linking of AAc inside cross-linked PP-g-PNIPAAm by a low gamma radiation dose of 2.5kGy. The films were characterized regarding the amount of grafted polymers and their composition (FTIR-ATR), thermal behavior (DSC), temperature- and pH-responsive swelling and contact angle (critical pH 6 and lower critical solution temperature ∼33°C), and loading and release rate of vancomycin. Drug loading was driven by specific interactions between vancomycin and PAAc. Drug-loaded films sustained the delivery for several hours at pH 7.4 and provided release rate values adequate for killing bacteria attempting to adhere the surface of the films.
Keywords: Interpenetrating network (IPN); Surface modified polypropylene; Smart medical devices; Stimuli-responsive drug release; Vancomycin delivery
Synthesis and properties of novel aliphatic poly(carbonate-ester)s
by Yu Zhou; Guang-Liang Wu; Ren-Xi Zhuo; Zhi-Lan Liu (pp. 1868-1872).
The biodegradable poly(5-methyl-5-methoxycarbonyl-1,3-dioxan-2-one- co-d,l-lactide) [poly(MMTC- co-d,l-LA)] copolymers were synthesized by the ring-opening copolymerization. The results show that the yield and molecular weight of copolymers are significantly influenced by reaction conditions. The chemical structure of the resultant copolymers was characterized by FTIR,1H NMR and13C NMR methods. Their molecular weight was measured by gel permeation chromatography (GPC). Study of monomer coreactivity ratios indicates thatd,l-LA reacts faster than MMTC in the copolymerization. The enzymatic degradation of the polymers with various compositions was studied at 37°C in pH=8.6 Tris–HCl buffer solution in the presence of proteinase K. Their mechanical properties were also preliminarily investigated.
Keywords: Biodegradable; Polycarbonates; Polyesters; Proteinase K; Ring-opening polymerization
Comparison of redox initiated graft polymerisation and sulfonation for hydrophilisation of polyethersulfone nanofiltration membranes
by B. Van der Bruggen (pp. 1873-1882).
Three polyethersulfone nanofiltration membranes, including two commercial membranes (NFPES10 and N30F) and one lab-made membrane (N71), were hydrophilised in view of an increased water flux and a reduction of membrane fouling.Non-modified as well as modified membranes were characterized using contact angle measurements, water fluxes and retention of sugars.At first, redox initiated graft polymerization was applied, and the influence of reaction time, initiator concentration and monomer concentration were investigated. It was observed that grafting always resulted in a significant reduction of the contact angle. The higher the reaction time, the lower was the contact angle, but the initiator and monomer concentration had no effect when above a threshold value. Grafting results in a decrease of the water flux, while the retention of raffinose increased.A comparison was made with the addition of sulfonated polyethersulfone to the polymer solution. By blending polyethersulfone and sulfonated polyethersulfon, a sufficiently high viscosity could be achieved. The influence of the blending ratio was investigated. The larger the fraction of sulfonated polyethersulfon, the more hydrophilic the membrane became. The addition of sulfonated polyethersulfon, however, has also an influence on the water flux and on the retention of sugars. An important conclusion is also that the membranes containing sulfonated polyethersulfone are significantly more hydrophilic than the ones that have been modified through the grafting technique.
Keywords: Poly(ether)sulfone; Nanofiltration; Membranes; Modification; Hydrophilicity; Surface characteristics
Linear nano-templates of styrene and maleic anhydride alternating copolymers
by Thomas D. Lazzara; Michael A. Whitehead; Theo G.M. van de Ven (pp. 1883-1890).
Poly(styrene-alt-maleic anhydride) (SMA) self-assembles in aqueous solution to form nanotube structures. These can be used as templates to linearly guide the growth of a secondary polymeric or inorganic material. Templates are made starting from a basic SMA solution, followed by slow pH decrease by dialysis against deionized water, until a 50% degree of protonation is reached. The nanotube structure is composed of multiple polymer chains, associating sideways by π-stacking to form the nanotube walls. The SMA templates were used to grow linear composites, which shows the applicability of the template properties and also confirms the nanotube association mechanism. Linear polymer composites were formed using this SMA template: pyrrole was polymerized, silver nitrate was reduced to silver and silver cyanide nanowires were grown.
Keywords: Nanotube; Template; Self-assembly; Polymer π-stacking; Nanocomposites
Compressibility and thermal expansion coefficients of nanocomposites with amorphous and crystalline polymer matrix
by L.A. Utracki (pp. 1891-1903).
Clay-containing polymeric nanocomposites (CPNC) with polystyrene (PS) or polyamide-6 (PA-6) matrix were studied within T=300–600K and P=0.1–190MPa. From the Pressure–Volume–Temperature ( PVT) data the derivatives: compressibility, κ, and thermal expansion coefficient, α, were computed as functions of T, P and clay content, w. Dependence of these coefficients on P and T were significantly different for the amorphous PS than for the semi-crystalline PA-6. In the PS plots of κ and α vs. T the presence of secondary transitions, Tβ/ Tg≈0.9±0.1 and Tc/ Tg=1.2±0.1, were detected and the clay effect at low T was prominent, affecting the physical aging. The isobaric values of α= α( T) were characterized by nearly T-independent values in the glassy and molten phase, connected by a large transitory region stretching from the ambient pressure values of Tg to Tc; this region was even more prominent in κ=κ( T). The derivative properties of PA-6 based CPNC were distinctly different. Here, the isobaric κ=κ( T) followed the same dependence on both sides of the melting zone, while the isobaric α= α( T) dependencies were dramatically different for the solid and molten phase; at T< Tm α linearly increased with T, after melting its value sharply decreased, and then at T> Tm (depending on w and P) either increased or decreased with T. Interpretation of the behavior in the melt and glass is based on the Simha–Somcynsky (S–S) cell-hole theory while that of the semicrystalline state on the Midha–Nanda–Simha–Jain (MNSJ) cell theory. In spite of the nonequilibrium conditions below the main transition point, Tg or Tm, the theories well predict the observed dependencies.
Keywords: Thermal expansion coefficient; Compressibility coefficient; Polyamide-6; Polystyrene; NanocompositesAbbreviations; 3D; three dimensions; ADA; ω-amino dodecyl acid; Bcc; body-centered cubic packing; CPNC; clay-containing polymeric nanocomposites; eos; equation of state; fcc; face-centered cubic packing; hcp; hexagonal close packing; LDPE; low density polyethylene; L–J; Lennard–Jones; MCT; mode-coupling theory; MNSJ; Midha–Nanda–Simha–Jain cell eos of crystalline phase; MMT; montmorillonite; PA-6; poly-ε-caprolactam; PS; polystyrene; PVT; pressure–volume–temperature dependence; SEM; scanning electron microscopy; S–S; Simha–Somcynsky cell-hole theory or eos; TFT; twinkling fractal theory; VFTH; Vogel–Fulcher–Tammann–Hesse (see Eq. 5); XRD; X-ray diffraction
Mechanical properties of attapulgite clay reinforced polyurethane shape-memory nanocomposites
by Bin Xu; W.M. Huang; Y.T. Pei; Z.G. Chen; A. Kraft; R. Reuben; J.Th.M. De Hosson; Y.Q. Fu (pp. 1904-1911).
Nanocomposites based on attapulgite clay and shape-memory polyurethane were fabricated by mechanical mixing. The mechanical properties of samples were evaluated using a micro-indentation tester. The untreated commercial attapulgite clay resulted in a significant decrease in glass transition temperature and hardness of the nanocomposite due to the presence of moisture as well as the clay’s amorphous structure and surface hydroxyl groups. The attapulgite nanoparticles were heat-treated at 850°C, which resulted in crystallization of the particles and formation of layered attapulgite structure. The hardness of the nanocomposites composed of the heat treated clay powder dramatically increased as a function of clay content, which is attributed to the homogeneous dispersion of the nanofillers in the polymer matrix and strong filler–polymer interactions. Shape recovery of indentations has been demonstrated upon heating.
Keywords: Shape memory; Nanocomposites; Polyurethane; Nano-clay; Vickers indentation; Microhardness
Introduction of Quantum Dots into PNIPAM microspheres by precipitation polymerization above LCST
by Dominik Jańczewski; Nikodem Tomczak; Ming-Yong Han; G. Julius Vancso (pp. 1912-1917).
Amphiphilic polymers having different polymerizable functional groups were synthesised and investigated as coatings for semiconductor nanoparticles (Quantum Dots, QDs). QDs coated with hydrophobic ligands were successfully transferred into water using these polymers and the assemblies were co-polymerized with N-isopropylacrylamide (NIPAM) by a precipitation polymerization method. In the resulting hybrid microspheres, QDs were uniformly distributed within the PNIPAM matrix. The influence of different polymerizable groups and counter ions of the amphiphilic polymer on the copolymerization process were investigated.
Keywords: Quantum Dot (QD); Amphiphilic polymer; PNIPAM; Microgels
Preparation of intermediary layer crosslinked micelles from a photocrosslinkable amphiphilic ABC triblock copolymer
by Jin Sook Kim; Hyun Jeong Jeon; Mi Seon Park; Young Chang You; Ji Ho Youk (pp. 1918-1923).
To prepare intermediary layer crosslinked micelles, a photocrosslinkable amphiphilic ABC triblock copolymer, poly(ethylene glycol)- b-poly(2-cinnamoyloxyethyl methacrylate)- b-poly(methyl methacrylate) (PEG–PCEMA–PMMA), was synthesized and its micellar characteristics were investigated. The triblock copolymer of PEG- b-poly(2-hydroxyethyl methacrylate)- b-PMMA (PEG–PHEMA–PMMA) ( Mn=9800g/mol, Mw/ Mn=1.33) was first polymerized by activators generated by electron transfer (AGET) atom transfer radical polymerization (ATRP) using a PEG macroinitiator in a mixed solvent of anisole/2-isopropanol (3/1 v/v). The middle block of the copolymer was then functionalized with cinnamoyl chloride. The degrees of polymerization of the PEG, PHEMA, and PMMA blocks were 113, 18 and 21, respectively. The critical micelle concentration (CMC) of the PEG–PCEMA–PMMA was 0.011mg/mL. The PEG–PCEMA–PMMA micelles were spherically shaped with an average diameter of 43nm. The intermediary layer of the PEG–PCEMA–PMMA micelles was crosslinked by UV irradiation. Not all of the cinnamate groups underwent photocrosslinking probably due to a lack of other cinnamate groups in their immediate vicinity. However, the degree of photocrosslinking of the intermediary layer of the PEG–PCEMA–PMMA micelles was sufficient to give excellent colloidal stability, even in different external environments.
Keywords: Amphiphilic ABC triblock copolymer; Atom transfer radical polymerization (ATRP); Photocrosslinkable micelle; Intermediary layer; Cinnamate group
Hydrogen bond mediated supramolecular micellization of diblock copolymer mixture in common solvents
by Shiao-Wei Kuo; Pao-Hsaing Tung; Feng-Chih Chang (pp. 1924-1935).
We report a new approach toward preparing self-assembled hydrogen-bonded complexes having vesicle and patched spherical structures from two species of block copolymers in nonselective solvents. Two diblock copolymers, poly(styrene- b-vinyl phenol) (PS- b-PVPh) and poly(methyl methacrylate- b-4-vinylpyridine) (PMMA- b-P4VP), were synthesized through anionic polymerization. The assembly of vesicles from the intermolecular complex formed after mixing PS- b-PVPH with PMMA- b-P4VP in THF was driven by strong hydrogen bonding between the complementary binding sites on the PVPH and P4VP blocks. In contrast, well-defined patched spherical micelles formed after blending PS- b-PVPh with PMMA- b-P4VP in DMF: the weaker hydrogen bonds formed between the PVPh and P4VP blocks in DMF, relative to those in THF, resulted in the formation of spherical micelles having compartmentalized coronas consisting of PS and PMMA blocks.
Keywords: Diblock copolymer; Self-assembly; Hydrogen bonding; Micelle
The effect of the resultant microphase-separated structures of polymer matrices on the electro-optical properties of polymer dispersed liquid crystal films by Iniferter polymerization
by Bin Yan; Jie He; Yuqing Fang; Xin Du; Qin Zhang; Shoulian Wang; Cuihong Pan; Yinghan Wang (pp. 1936-1940).
Iniferter polymerization was employed to prepare polymer dispersed liquid crystal (PDLC) films and an additional photoinitiator was introduced to induce the phase separation of polymer matrices themselves on the process of preparing the PDLC. The effect of the polymerization kinetics and the resultant microphase-separated structures of polymer matrices on the electro-optical properties of PDLC films were studied. It was found that the bigger length scale of phase separation of polymer matrices induced strong light-scattering resulting in low ON-state transmittance. And faster polymerization kinetic induced higher threshold and saturation voltages.
Keywords: Liquid crystal; Polymer dispersed liquid crystal; Polymerization induced phase separation; Electro-optical properties
Kinetics and thermal properties of epoxy resins based on bisphenol fluorene structure
by Zhen Dai; Yanfang Li; Shuguang Yang; Ning Zhao; Xiaoli Zhang; Jian Xu (pp. 1941-1948).
The fluorene-containing epoxy, diglycidyl ether of 9,9-bis(4-hydroxyphenyl) fluorene (DGEBF) was synthesized by a two-step reaction procedure. In order to investigate the relationship between fluorene structure and material properties, DGEBF and a commonly used diglycidyl ether of bisphenol A (DGEBA) were cured with 4,4-diaminodiphenyl methane (DDM) and 4,4-(9-fluorenylidene)-dianiline (FDA). The curing kinetics, thermal properties and decomposition kinetics of these four systems (DGEBA/DDM, DGEBF/DDM, DGEBA/FDA, and DGEBF/FDA) were studied in detail. The curing reactivity of fluorene epoxy resins was lower, but the thermal stability was higher than bisphenol A resins. The onset decomposition temperature of cured epoxy resins was not significantly affected by fluorene structure, but the char yield and Tg value were increased with that of fluorene content. Our results indicated that the addition of fluorene structure to epoxy resin is an effective method to improve the thermal properties of resins, but excess fluorene ring in the chain backbone can depress the curing efficiency of the resin.
Keywords: Epoxy resins; Fluorene; Thermal properties; Kinetics
Comparative non-isothermal kinetic analysis of thermal degradation of poly(vinyl chloride) prepared by living and conventional free radical polymerization methods
by P.N. Simões; Jorge F.J. Coelho; Pedro M.F.O. Gonçalves; M.H. Gil (pp. 1949-1959).
Non-isothermal kinetics of the thermal degradation of poly(vinyl chloride) (PVC) prepared by a living radical polymerization (LRP) method was performed and compared with the results obtained from PVC prepared by the conventional free-radical process (FRP). Both differential and integral isoconversional methods were applied for determining the apparent activation energy of the dehydrochlorination stage. This study made clear noticeable differences in the thermal degradation of the PVC samples under analysis. The newly synthesized LRP-PVC material has a better thermal stability and presents substantial differences in the macroscopic kinetics of the dehydrochlorination process compared with conventional FRP-PVC. These differences were assessed in quantitative terms on the basis of the kinetic triplet[Ea,A,f(α)].
Keywords: Poly(vinyl chloride) (PVC); Living radical polymerization (LRP); Thermal decomposition; Non-isothermal kinetic analysis
Macromolecular conjugate based particulates: Preparation, characterisation and evaluation of controlled release properties
by Liyan Zhang; Anitha Dudhani; Leif Lundin; Shantha L. Kosaraju (pp. 1960-1969).
A new particulate delivery matrix based on macromolecular conjugate, chitosan–whey protein isolate ([Ch–WPI]) was found to exhibit controlled release properties. Fourier-Transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) demonstrated the formation of the conjugate. Particle formation of the conjugate was carried out by the ionic crosslinking technique using sodium tripolyphospate (STP). Catechin entrapped particles were prepared by varying the weight ratios of STP to conjugate [Ch–WPI]. Both the placebo and catechin-entrapped particles were found to be positively charged below pH 7.2, indicating their stability to aggregation and their suitability for bioadhesion in the gastrointestinal tract (GIT). The entrapment efficiencies of the particles ranged between 29% and 42% for particles prepared using different weight ratios of the conjugate to STP. There was 34–56% of catechin release in simulated GIT conditions depending on the entrapment efficiencies and the degree of crosslinking of the particles.
Keywords: Chitosan; Whey protein isolate; Catechin; Controlled release
The chiral effects on the responses of osteoblastic cells to the polymeric substrates
by Qiangying Yi; Xiantao Wen; Li Li; Bin He; Yu Nie; Yao Wu; Zhirong Zhang; Zhongwei Gu (pp. 1970-1978).
In order to study the chiral effects of polylactides on responses of osteoblastic cells, poly(l-lactide) (PLLA), poly(d-lactide) (PDLA), poly(dl-lactide) (PDLLA) and the stereocomplex of PLLA and PDLLA (SC) films with different stereoforms were prepared. The surface properties of the four polylactide films were tested and the osteoblastic ROS 17/2.8 cells were cultured on the films. The protein adsorption behaviors of fibrinogen and bovine serum albumin on films were studied. The cell proliferation, total protein amount, DNA content and alkaline phosphatase activity of osteoblastic ROS 17/2.8 cells were evaluated. The results showed that the protein adsorption was dependant on the type of proteins. The observation of cell morphologies revealed that the PDLA film provide an unfavorable surface for cell attachment. The total protein amount, DNA content and ALP activity were closely related to the stereoforms of polylactide films. All the levels of total protein amount, DNA content and ALP activity of ROS 17/2.8 cells on PDLA film were decreased. The racemic stereocomplex of PLLA and PDLA showed relatively higher positive effects on both cell growth and proliferation.
Keywords: Chirality; Polylactide; Stereocomplex; Ros17/2.8 cells
Synthesis and characterization of well-defined poly( tert-butyl acrylate) star polymers
by Barbara Mendrek; Barbara Trzebicka (pp. 1979-1993).
Star polymers with different numbers and lengths of poly( tert-butyl acrylate) (PTBA) arms were obtained via atom transfer radical polymerization. Aliphatic alcohols with different number of hydroxyl groups varying from 3 to 6 and calixarenes based on pyrogallol with 12 and 16 phenol groups were transformed to bromoester derivatives to prepare multifunctional ATRP initiators used as the cores of the stars. The star polymers were characterized by GPC with refractive index, multiangle laser light scattering and viscosimetric detectors. The molar masses of the stars reached 70,000g/mol and the molar mass dispersities did not exceed 1.2. To elucidate the compact structure of the stars, their true molar masses were determined by GPC with triple detection (RI–MALLS–Visco) and compared with the apparent molar masses obtained from the calibration with linear poly( tert-butyl acrylate) standards. The intrinsic viscosities of the PTBA stars of the same molar mass decreased with the number of star arms but were always lower than the intrinsic viscosities of the analogue linear PTBA polymers. The values of the branching ratio g′ decreased with increasing number of arms indicating more compact structure of stars. The branching ratio g′ was correlated to the empirical predictions.
Keywords: Star polymers; Poly(; tert; -butyl acrylate); Gel permeation chromatography; Triple detection; Intrinsic viscosity; Branching parameter
Synthesis of a novel water-soluble polyamide dendrimer based on a facile convergent method
by Keita Endo; Yumiko Ito; Tomoya Higashihara; Mitsuru Ueda (pp. 1994-2001).
A novel, rapid, inexpensive, and highly efficient convergent approach has been developed for the synthesis of a 32-amine-terminated G3 polyamide dendrimer by the hydrolysis of the dendrimer with trifluoroacetamide groups. The resulting dendrimer could be successfully modified with oligo(ethylene glycol) chains at its periphery to afford a novel water-soluble polyamide dendrimer. The structural homogeneity of the dendrimers was confirmed by NMR and MALDI-TOF mass spectroscopies.
Keywords: Polyamide dendrimer; One pot synthesis; Convergent method; Water-soluble dendrimer
Luminescent polymeric hybrids functionalized by β-diketone with silicon–oxygen networks and carbon chains: Assembly and characterization
by Xiao-Fei Qiao; Bing Yan (pp. 2002-2010).
2-Thenoyltrifluoroacetone (TTA) was grafted onto the coupling agent 3-(triethoxysilyl)-propyl-isocyanate to construct the precursor I (TTA–Si), and polymer precursors II (PVPD, PMAA and PVPDMAA) were synthesized through the addition polymerization reactions. Then precursors I and II have coordinated to the rare-earth ions with the carbonyl, carboxyl group or nitrogen atom, respectively, and after hydrolysis and copolycondensation sol–gel process, the three kinds of polymeric hybrids were obtained. FTIR, ultraviolet–visible diffuse reflection and fluorescence absorption spectra, electronic micrographs, room-temperature X-ray diffraction patterns and TG plots were characterized and the results reveal that the hybrid materials showed uniformity in the microstructure, efficient intramolecular energy transfer system and excellent characteristic emission of terbium ions under UV irradiation.
Keywords: Polymeric hybrids; Rare-earth complex; Chemically bonded; Carbon chains; Photoluminescence
Microwave-assisted rapid decomposition of persulfate
by C. Costa; V.H.S. Santos; P.H.H. Araujo; C. Sayer; A.F. Santos; M. Fortuny (pp. 2011-2016).
Microwave irradiation has been a promising alternative to conduct several chemical reactions. In this work the microwave effects in potassium persulfate decomposition rate, under controlled conditions of temperature and microwave power, were evaluated. Higher decomposition rate constants were obtained in microwave irradiated reactions in comparison with conventional heated ones. To study the effect of high power microwave irradiation, a pulsed irradiation strategy was developed, in which the samples were repeatedly heated within short intervals of time at high power levels (500 or 1400W). A great decomposition percentage was achieved in shorter irradiation times, showing the kinetic advantages of microwave-assisted reactions. However, it was found no differences in the reaction yields, even when high power levels were involved, proving that microwave enhancements may arise only from the ability to quickly provide a large amount of energy to the reaction medium.
Keywords: Microwave irradiation; Persulfate decomposition; Kinetics; Emulsion polymerization
Chlorination and characterization of natural rubber and its adhesion to nitrile rubber
by Siriwat Radabutra; Sombat Thanawan; Taweechai Amornsakchai (pp. 2017-2022).
Chlorinated natural rubber (CNR) vulcanized sheets were prepared by immersing the NR sheets in sodium hypochlorite solution for various chlorination times ranging from 0 to 30min. The degree of chlorination as indicated by X-ray Absorption Near-Edge Spectroscopy (XANES) implied that the chlorine content increases with the chlorination time from 0 to 10min then levels off. Atomic Force Microscopy (AFM) showed an evolution of the surface roughness and stiffness. These two properties increased gradually with chlorination time. The bond strength between CNR and nitrile rubber (NBR) also increased gradually. The data showed cohesive failure beginning at 1min and extending throughout the 30min of the study. The maximum peel strength was found at 1min of chlorination time and decreased afterwards. The decrease in peel strength was caused by the increase in surface stiffness of NR that acted as weak boundary layer. The surface stiffness governed the peel strength between NR and NBR.
Keywords: Chlorination; Adhesion; XANES; AFM; NR; NBR
Synthesis of tri-layer hybrid microspheres with magnetic core and functional polymer shell
by Guangyu Liu; Hui Wang; Xinlin Yang; Longyu Li (pp. 2023-2032).
Tri-layer magnetite/silica/poly(divinylbenzene) (Fe3O4/SiO2/PDVB) core-shell hybrid microspheres were prepared by distillation precipitation polymerization of divinylbenzene (DVB) in the presence of magnetite/3-(methacryloxyl)propyl trimethoxysilane (MPS) modified silica core-shell particles as seeds. The polymerization of DVB was performed in neat acetonitrile with 2,2′-azobisisobutyronitrile (AIBN) as initiator to coat magnetite/MPS-modified silica particles through the capture of DVB oligomers with the aid of vinyl groups on the surface of inorganic seeds in absence of any stabilizer or surfactant. Other magnetite/silica/polymer tri-layer hybrid particles, such as magnetite/silica/poly(ethyleneglycol dimethacrylate) (Fe3O4/SiO2/PEGDMA) and magnetite/silica/poly(ethyleneglycol dimethacrylate- co-methacrylic acid) (Fe3O4/SiO2/P(EGDMA- co-MAA)) with various polarity and functionality, were also prepared by this procedure. Magnetite/silica/poly( N,N′-methylenebisacrylamide- co-methacrylic acid) (Fe3O4/SiO2/P(MBAAm- co-MAA)) were synthesized with unmodified magnetite/silica particles as seeds. The resultant tri-layer hybrid particles were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectra (FT-IR), dynamic light scattering, and vibrating sample magnetometer (VSM).
Keywords: Magnetite; Core-shell microsphere; Distillation precipitation polymerization; Tri-layer hybrid
Preparation and characterization of single-hole macroporous organogel particles of high toughness and superfast responsivity
by Deniz C. Tuncaboylu; Oguz Okay (pp. 2033-2042).
Crosslinked macroporous polymer particles containing a single large hole in their surfaces were prepared by solution crosslinking of butyl rubber (PIB) in benzene using sulfur monochloride (S2Cl2) as a crosslinking agent. The reactions were carried out within the droplets of frozen solutions of PIB and S2Cl2 at −18°C. Spherical millimeter-sized organogel beads with a polydispersity of less than 10% were obtained. The particles display a two phase morphology indicating that both cryogelation and reaction-induced phase separation mechanisms are operative during the formation of the porous structures. The beads exhibit moduli of elasticity of 1–4kPa, much larger than the moduli of conventional nonporous organogel beads formed at 20°C. The gel particles also exhibit fast responsivity against the external stimulus (solvent change) due to their large pore volumes (4–7ml/g). The gel beads prepared at −18°C are very tough and can be compressed up to about 100% strain during which almost all the solvent content of the particles is released without any crack development. The sorption–squeezing cycles of the beads show that they can be used in separation processes in which the separated compounds can easily be recovered by compression of the beads under a piston.
Keywords: Organogel beads; Macroporous particles; Butyl rubber; Cryogelation; Elasticity; Swelling
A new UV-curable powder coating based on a α,ω-unsaturated copolyamide 6/11/12
by Marion N’Negue Mintsa; Laurence Lecamp; Claude Bunel (pp. 2043-2052).
This work deals with the elaboration of a new UV-curable powder coating for heat sensitive substrates. This powder contains a α,ω-unsaturated copolyamide 6/11/12 having a melting point of 107°C and 4% (w/w) of photoinitiator. After description of the copolyamide synthesis, the photochemical reaction was investigated in the presence of two Norrish II photoinitiators (benzophenone and 4-phenylbenzophenone). The influence of the photocrosslinking on the crystallinity of the ultimate materials was studied. It was shown that the photochemical reaction can take place even when the sample is at the solid state and that its yield increases with the temperature and the time of irradiation. Lastly, the influence of the crystallinity/crosslinking ratio was characterized by measuring the swelling of the UV-cured materials into different solvents.
Keywords: UV-curable powder coating; Polyamide; Benzophenone; Undecylenic acid
Synthesis and properties of novel organosoluble polyimides derived from bis[3-(4-amino-2-trifluoromethylphenoxy) phenyl] ether
by Fengchun Yang; Jiujiang Zhao; Yanfeng Li; Shujiang Zhang; Yu Shao; Hao Shao; Tao Ma; Chenliang Gong (pp. 2053-2059).
A new aromatic ether diamine, bis[3-(4-amino-2-trifluoromethylphenoxy) phenyl] ether, was successfully synthesized via nucleophilic substitution reaction of 3,3′-oxydiphenol and 2-chloro-5-nitrotrifluoromethylbenzene, followed by a catalytic reduction. A series of new polyimides were synthesized from the diamine with various commercially available aromatic dianhydrides via a conventional two-stage process, i.e. ring-opening polyaddition forming the poly(amic acid)s and further thermal or chemical imidization forming polyimides. The resulting polyimides exhibited good solubility in polar solvents, such as N,N-dimethylacetamide, N,N-dimethylformamide, N-methyl-2-pyrrolidinone and common solvents such as chloroform, tetrahydrofuran upon heating and possessed the inherent viscosities of 0.51–0.68dL/g. The resulting strong and flexible films exhibited excellent thermal stability with the temperature at 10% weight loss is above 502°C and the glass transition temperature in the range of 191–232°C. The polyimides also were found to possess high optical transparency.
Keywords: Polyimides; Diamine monomer; Solubility; Optical properties
Thermo- and pH-sensitive comb-type grafted poly( N, N-diethylacrylamide-co-acrylic acid) hydrogels with rapid response behaviors
by Hongliang Liu; Mingzhu Liu; Liwei Ma; Jun Chen (pp. 2060-2067).
Poly( N, N-diethylacrylamide) with a terminal hydroxyl end group (PDEA-OH) was synthesized by radical telomerization of N, N-diethylacrylamide (DEA) monomer using 2-hydroxyethanethiol as a chain transfer agent. Macromonomer of thermo-sensitive PDEA was synthesized by condensation reaction of PDEA-OH with acryloyl chloride. The macromonomer was characterized by FTIR and1H NMR, and the molecular weight was determined by GPC. Thermo- and pH-sensitive comb-type grafted poly( N, N-diethylacrylamide-co-acrylic acid) (PDEA-co-AA) hydrogels (GHs) were successfully prepared by grafting PDEA chains with freely mobile ends onto the backbone of a cross-linked (PDEA-co-AA) network. The results showed that the deswelling behavior of the hydrogels was dependent on the test temperature. At 45°C (beneath the VPTT of the hydrogels), both the normal-type hydrogels (NHs) and comb-type grafted P(DEA-co-AA) hydrogels had lower deswelling rates. While at 60°C (far beyond the VPTT of the hydrogels), the deswelling rates of the GHs were faster than that of the NHs. Furthermore, pulsatile stimuli-responsive studies indicated that the GHs had excellent thermo-reversibility and were superior to the NHs in the magnitude of their swelling ratios to temperature changes. However, the reversibility to pH changes was poor for both the NHs and the GHs.
Keywords: Hydrogel; Graft; Poly(; N,N; -diethylacrylamide-co-acrylic acid); Rapid response
The influence of molecular orientation on the crosslinking/oxidative behaviour of iPP exposed to gamma radiation
by E. Suljovrujic (pp. 2068-2078).
This paper presents a study of the influence of structural peculiarities, uniaxial orientation and fibrillar structure on the radiation-induced changes in iPP. For the purposes of this study, iPP was oriented via solid-state stretching at elevated temperature to various draw ratios and, later on, gamma irradiated in air. In order to investigate orientation- and/or radiation-induced structural changes, optical microscopy (OM), scanning electron microscopy (SEM), wide angle X-ray scattering (WAXS), differential scanning calorimetry (DSC), infrared spectroscopy (IR) and gel measurements were employed. To quantify the degree of molecular orientation, Herman’s orientation function (f c), was used. IR spectroscopy and gel measurements were used to determine the changes in the oxidative degradation and degree of network formation, respectively. Sol–gel analysis was studied in detail using the Charlesby–Pinner (C–P) equation. The radiation-induced changes in the structure and evolution of oxygen-containing species were also studied through dielectric loss (tan δ) analysis in a wide frequency range; the polar groups that were introduced by irradiation in apolar iPP were considered as tracer groups. Conclusions derived according to different methods were compared. Presented results reveal two different radiation-induced dynamics; gamma irradiation of initial and fully developed fibrillar iPP structures leads to significantly different crosslinking and/or oxidation response.
Keywords: Gamma irradiation; Orientation; Polypropylene; Crosslinking
Effect of oxadiazole side chains based on alternating fluorene–thiophene copolymers for photovoltaic cells
by Bin Zhao; Daxi Liu; Li Peng; Hui Li; Ping Shen; Na Xiang; Yijiang Liu; Songting Tan (pp. 2079-2086).
Three soluble alternating conjugated copolymers, comprised of 9,9-dihexylfluorene and thiophene derivatives with/without oxadiazole side chains, were synthesized via the palladium-catalyzed Suzuki coupling reaction. The structures of the polymers were confirmed with1H NMR and13C NMR, and the effect of oxadiazole side chains on the thermal, optical, electrochemical and photovoltaic properties were investigated. The introduction of rigid oxadiazole side chains could benefit to improve thermal stabilities of the conjugated polymers. Cyclic voltammograms revealed that the LUMO energy levels of P2 and P3 were reduced in comparison with P1 due to the introduction of electron-deficient oxadiazole side chains, indicating that electron-injection and transporting properties have been improved. Photovoltaic cells (PVCs) were fabricated based on the blend of the as-synthesized copolymers and the fullerene acceptor [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) in a 1:1 weight ratio. The maximum power conversion efficiency (PCE=1.49%) was obtained for P3 as the electron donor under the illumination of AM 1.5, 100mW/cm2.
Keywords: Conjugated polymers; Fluorene; Oxadiazole; Solar cells; Suzuki coupling reaction; Thiophene
Photocurable oligo(hemiacetal ester)s having methacrylate side chains
by Daisaku Matsukawa; Tomoya Mukai; Haruyuki Okamura; Masamitsu Shirai (pp. 2087-2095).
Two types of oligo(hemiacetal ester)s which have methacrylate units and tertiary ester linkages in the side chains were synthesized by polyaddition of corresponding dicarboxylic acid with divinyl ether. One oligomer has a ortho linked main-chain structure, and the other one has meta and para linked main-chain structure. These oligomers were applied to a photocrosslinking system having photo/thermal degradable properties. On UV irradiation at 365nm under N2 atmosphere, oligomer films containing methyladamantyl methacrylate (MADMA), 2,2-dimethoxy-2-phenylacetophenone (DMPA), triphenylsulfonium triflate (TPST) became insoluble in acetone. Insolubilization behavior was not influenced by the difference of main-chain structure. When the crosslinked oligomer/MADMA films were irradiated at 254nm and followed by baking, they became soluble in acetone. The effective baking temperature depended on the oligomer structure. The cleavage of hemiacetal ester and tertiary ester linkages was confirmed by FT-IR spectroscopy.
Keywords: Photocrosslinking; De-crosslinking; Thermal degradation; Oligo(hemiacetal ester)s; Polyaddition
Synthesis and microstructure–mechanical property relationships of segmented polyurethanes based on a PCL–PTHF–PCL block copolymer as soft segment
by L. Rueda-Larraz; B. Fernandez d’Arlas; A. Tercjak; A. Ribes; I. Mondragon; A. Eceiza (pp. 2096-2109).
The goal of this work has been the synthesis of novel materials based on a biodegradable polycaprolactone-block–polytetrahydrofurane-block–polycaprolactone diol (PCL-b–PTHF-b–PCL). The segmented thermoplastic polyurethanes (STPU) have been synthesised in bulk without catalyst at different molar ratios and their characterization has been performed by different techniques. The physic-chemical interactions, responsible for the unique polyurethane properties, have been evaluated by total attenuated Fourier transform infrared spectroscopy (ATR-IR) in the amide I region using a Gaussian deconvolution technique and, on the other hand, atomic force microscopy (AFM) has been employed to determine the phase microstructures. The effect of increase the hard segment content (HS) has been discussed from the viewpoint of the miscibility of hard and soft segments, analyzed by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). The influence of HS content on the microstructure–mechanical property relationships has also been investigated. Special attention has been focused on the wettability of the samples, measured through water contact angle measurements (WCA), to determine the tendency for biocompatibility of the samples.
Keywords: Segmented polyurethanes; Microstructure–property relationships; Water contact angle; Atomic force microscopy
Flow induced crystallization of long chain branched polypropylenes under weak shear flow
by Fengyuan Yu; Hongbin Zhang; Ruogu Liao; Hong Zheng; Wei Yu; Chixing Zhou (pp. 2110-2118).
In the present work long chain branched polypropylene (LCB PP) polymers were prepared by linear polypropylene and multi-functional monomer through melt grafting reaction. A quantitative rheological method was adopted to analysis the structure parameters of LCB PP. The effects of chain branched level on the crystallization kinetics of PP were investigated by rheology, differential scanning calorimetry, polarized optical microscope and wide-angle X-ray diffraction. The dynamic viscoelastic properties of LCB PP showed that the increase in the chain branched level caused a typical deviation from the terminal behavior and a different distribution of the melt relaxation spectrum in the long relaxation time regime. It was found that the chain branched level had a significant effect on the flow induced crystallization (FIC) process of PP melts. The crystallization of LCB PP was more sensitive to shear flow than that of linear PP during induced period at low shear rates. This result also indicated that the longer relaxation time of the polymer chains played an important role in the nucleation of PP under shear flow fields. LCB PP with high chain branched level showed accelerated crystallization kinetics in comparison with that with low chain branched level.
Keywords: Polypropylene; Long chain branching (LCB); Flow induced crystallization; Crystallization kinetics
Study on metal complexes of chelating resins bearing iminodiacetate groups
by Ecaterina Stela Dragan; Maria Valentina Dinu; Gabriela Lisa; Andrzej W. Trochimczuk (pp. 2119-2130).
Cu(II), Co(II) and Ni(II) complexes of chelating resins (CR) bearing iminodiacetate (IDA) ligands were prepared. The CR-metal complexes were characterized by FT-IR spectroscopy, X-ray diffraction (XRD), thermal behavior (TG and DTG) under nitrogen atmosphere, and electron paramagnetic resonance (EPR). FT-IR spectra of the CR-metal complexes showed the characteristic bands of CR were still present but red-shifted after the metal complexation, and new bands assigned to Me–N bonds were observed. Thermal behavior of the metal-CR complexes supported the metal complexation, metal complexation leading to the decrease of the thermal stability of the CR, the lowest thermal stability being found when the highest amount of Cu(II) was loaded. Based on the EPR results and the thermal behavior of Cu(II)-CR complexes, the scheme for the complexation of Cu(II) on the CR was suggested.
Keywords: Chelating resins; Polymer-metal complexes; FT-IR spectroscopy; Thermogravimetric analysis; Electron paramagnetic resonance
Light-driven fluorescence enhancement of phenylazo indazole-terminated polystyrene
by Fang Ma; Nianchen Zhou; Jian Zhu; Wei Zhang; Lijuan Fan; Xiulin Zhu (pp. 2131-2137).
The well-defined phenylazo indazole-terminated polystyrene (PS) was successfully prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization of styrene (St) mediated by a novel chain transfer agent (CTA) bearing phenylazo indazole moieties in the Z group, benzyl-5-(4-(dimethylamino)phenylazo) indazole-1-carbodithioate (BPCD). The fluorescence emission of BPCD and the phenylazo indazole-terminated PS in chloroform (CHCl3) before and after the 365nm ultraviolet irradiation was investigated. Interestingly, the fluorescence intensities of BPCD and the phenylazo indazole-terminated PS in CHCl3 were both sensitive to the 365nm ultraviolet irradiation. The fluorescence intensities of these solutions increased with the irradiation time and reached maximum at 110min. The light-driven fluorescence enhancement of BPCD and the phenylazo indazole-terminated PS were both attributed to the formation of spherical aggregate originated from the trans–cis isomerization of azobenzene moieties in BPCD and PS chain, which was confirmed by transmission electron microscopy (TEM),1H NMR, UV and dynamic light scattering (DLS) spectra.
Keywords: Azo polymers; Fluorescence; Reversible addition-fragmentation chain transfer (RAFT); Self-assembly
Ethylene polymerization promoted by dinuclear titanium p-tert-butylthiacalixarene complexes
by Antonio Proto; Francesca Giugliano; Carmine Capacchione (pp. 2138-2141).
The dinuclear titanium p-tert-butylthiacalixarene complexes1 and2 after activation with methylaluminoxane have been tested as homogeneous catalysts for the polymerization of ethylene. The results show that the catalytic activity of1, although still poor, is higher than those of the related mononuclear titanium complexes bearing calixarene as ligand. The molecular weight of the polyethylene produced are high ( MW up to 1.4×106Dalton) with broad molecular weight distribution. The polyethylenes have high melting point (133–142°C) indicating a linear polymer microstructure which was confirmed by13C NMR analysis.
Keywords: Ziegler–Natta polymerization; Ethylene; Post-metallocene; Thiacalixarene
Effect of substituents on addition polymerization of norbornene derivatives with two Me3Si-groups using Ni(II)/MAO catalyst
by M.L. Gringolts; M.V. Bermeshev; K.L. Makovetsky; E.Sh. Finkelshtein (pp. 2142-2149).
Addition polymerization and copolymerization of bis(Me3Si)-substituted norbornene-type monomers such as 5,5-bis(trimethylsilyl)norbornene-2, 2,3-bis(trimethylsilyl)norbornadiene-2,5 and 3,4-bis(trimethylsilyl)tricyclo[4.2.1.02,5]nonene-7, in the presence of Ni(II) naphtenate/MAO catalyst were studied. Disubstituted norbornene and norbornadiene were found to be practically inactive in homopolymerization. On the other hand, their copolymerization with norbornene proceeded with moderate yields of copolymers containing predominantly norbornene units. Under studied reaction conditions 2,3-bis(trimethylsilyl)norbornadiene-2,5 was transformed into the only exo-trans-exo-dimer as a result of the [2+2]-cyclodimerization reaction. Moving Me3Si-substituents one carbon atom away from norbornene double bond made 3,4-bis(trimethylsilyl)tricyclo[4.2.1.02,5]nonene-7 active in homopolymerization and allowed to obtain addition homo-polymer with two Me3Si-substituents in each elementary unit. The reaction mechanism and steric effect of Me3Si-substituents are also discussed.
Keywords: Addition polymerization and copolymerization; Silyl-substituted polynorbornenes; Poly(tricyclononenes); [2+2]-Cyclodimerization; Ni-catalysts