Miscibility behaviour of sulfonylated poly(2,6-dimethyl-1,4-phenylene oxide) copolymers in the blends with poly(styrene-co-maleic anhydride) and with poly(α-methylstyrene-co-maleic anhydride)

Summary The miscibility behaviour of sulfonylated poly(2,6-dimethyl-1,4-phenylene oxide) of the different degree of sulfonylation blended with poly(styrene-co-maleic anhydride) or poly(-methylstyrene-co-maleic anhydride) was studied. The critical degree of sulfonylation for phase separation in these blends was found to be 55 mole % and 66 mole %, respectively. The miscibility behaviour was analyzed on the basis of the mean field treatment and studied by DSC.Dedicated to Professor Dragutin Fle in honor of his 70th birthday     

Miscibility of poly(styrene-co-vinyl phenol) with poly(ɛ-caprolactone)

Summary Poly(styrene-co-vinyl phenol) (STVPh)/poly(-caprolactone)(PCL) blends showed enhanced miscibility over polystyrene/PCL blend, and showed single glass transition temperature when the contents of vinyl phenol (VPh) in copolymer were higher than 10 wt % (maximum content of VPh in STVPh used in this study was 20 wt%). STVPh 4, STVPh 7, STVPh 10 (4, 7, 10 were VPh wt%)/PCL blends showed cloud points on heating for miscible blend system, and this phase separation was reversible on cooling. From melting point depression of PCL, interaction parameter, B. for miscible STVPh 12/PCL blend system was evaluated.     

Syntheses of diblock copolymers: poly(2-methylpropene)-b-poly(α-amino acid)

Summary Diblock copolymer poly (2-methylpropene)-b-poly (-amino acid) was obtained by polymerization of the corresponding N-caboxy anhydride initiated by a poly (2-methylpropene) bearing a terminal amine in dioxane/CH₂Cl₂ mixture. Copolymers were analyzed by FT IR, ¹H and ¹³C NMR. of the -amino acid segment determined by ¹H NMR fits well with those obtained by a theoretical calculation.     

Diazotization–cyanation of aromatic amines with crosslinked poly(4-vinylpyridine)-supported cyanide ions

A simple, mild, and efficient method for the cyanation of stable arenediazonium salts was developed with polymer-supported cyanide. Arenediazonium hydrogen sulfate (Ar N₂⁺HSO₄⁻) was obtained by the reaction between a primary aryl amine and sodium nitrite in the presence of concentrated sulfuric acid (H₂SO₄) at low temperature (0–5°C). By an ion-exchange reaction between Ar N₂⁺HSO₄⁻ and NaBF₄, the stable arenediazonium tetrafluoroborate, Ar N₂⁺BF₄⁻, was prepared. Ar N₂⁺BF₄⁻ was then converted to aryl nitrile with crosslinked poly(4-vinylpyridine) supported cyanide ion in acetonitrile at room temperature. The spent polymeric reagent was regenerated and reused several times without any loss in its activity. This procedure offered advantages, including a higher isolated yield, shorter reaction time, and simple reaction workup. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Nanosized micelles self-assembled from amphiphilic poly(citric acid)–poly(ε-caprolactone)–poly(citric acid) copolymers

In this study, novel ABA-type amphiphilic copolymers consisting of poly(citric acid) (PCA) (A) as hydrophilic segment and poly(ε-caprolactone) (PCL) (B) as hydrophobic block were prepared by an approach in the following two steps: (1) ring-opening polymerization (ROP) of ε-caprolactone with 1,5-pentanediol initiator to obtain a hydroxyl telechelic PCL; (2) melt polycondensation reaction of hydroxyl telechelic PCL and citric acid molecules. The prepared copolymers are capable of self-assembling into nanosized micelles in aqueous solution. The influence of the copolymer composition on the micelle dimensions was investigated. The critical micellar concentration of the copolymers is in the range of 5–6.3 × 10^?2 mg/mL which is determined by the fluorescence probe technique using pyrene. Also the results indicate that CMC of self assembled micelles is influenced by the hydrophilicity of PCA–PCL–PCA copolymers depending on the CA/CP ratio, and these micelles may find great potential as drug carriers in biomedical fields.     

Intercalative redox polymerization and characterization of poly(4-vinylpyridine)–vermiculite nanocomposite

A new nanocomposite material consisting of poly(4-vinylpyridine) (PVP) and vermiculite is synthesized by the intercalative redox polymerization of VP in the gallery of copper(II) ion-exchanged vermiculite. The formation of a single filament of the polymer in the gallery is confirmed by the increase in gallery spacing of 4.7 Å as indicated by X-ray diffraction (XRD) analysis. Electron spin resonance studies confirm the presence of Cu(II) upon ion exchange and its absence following redox polymerization. The amount of polymer present in the gallery is found to be ∼18–19 mass % by thermogravimetric analysis. Confining the polymer to the gallery spacing in vermiculite results in enhanced thermal stability that is evident from the increase in the initial decomposition temperature by ∼300°C. Differential scanning calorimetry of the nanocomposite indicates that the polymer is confined to a restricted geometry because of the absence of a glass-transition temperature, which confirms the XRD finding. The IR absorption peaks corresponding to PVP and the expected PVP UV π–π* transition at 275 nm, along with the XRD and thermal data confirms that the gallery expansion is due to the PVP filament. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 555–561, 2001     

Crystallization behavior of poly(β-propiolactone)-block-polyethylene copolymers with varying polyethylene crystallinities

The crystallization behavior of poly(β-propiolactone)-block-polyethylene (PPL-b-PE) copolymers with high PE crystallinities χ_PE (>0.30) has been examined using time-resolved synchrotron small-angle X-ray scattering and Fourier transform infrared spectroscopy, where the PE block crystallized first and subsequently the PPL block crystallized on quenching from a strongly segregated melt. The crystallization of PE blocks destroyed the lamellar microdomain structure (LMS) existing in the melt to form the crystalline lamellar morphology (CLM), and then PPL blocks crystallized within CLM. This morphology formation was compared to our previous results for the crystallization of PPL-b-PE copolymers with low χ_PE (0.12 < χ_PE < 0.26), where the crystallizability of PE blocks was not sufficiently large to destroy LMS. As a result, PE blocks crystallized promptly within LMS to reinforce and stabilize it against the subsequent crystallization of PPL blocks, yielding the confined crystallization of both blocks within LMS. We summarize these results including the case of χ_PE = 0, and propose three mechanisms of morphology formation occurring in PPL-b-PE copolymers according to χ_PE (i.e., high, low, or zero).     

Preparation and sorption studies of microsphere copolymers containing β-cyclodextrin and poly(acrylic acid)

Microsphere polymeric materials containing β-cyclodextrin (β-CD) and poly(acrylic acid) (PAA) with tunable morphologies were prepared in order to improve their sorption characteristics in aqueous solution. The microsphere polymeric materials were prepared using a (water/oil) micro-emulsion-evaporation technique to condense β-cyclodextrin (β-CD) with PAA at various comonomer ratios and mixing speeds. The β-CD microsphere copolymers were characterized using FTIR, TGA, DSC, SEM, elemental (C and H) microanalyses, and solid state ¹³C-NMR spectroscopy. The sorption properties of the polymeric materials at 295 K in aqueous solution containing p-nitrophenol (PNP) were studied using a dye-based method with UV–Vis spectrophotometry at pH 4.6 and 10.3. The sorption isotherms of copolymer/PNP systems were evaluated with various isotherm models (e.g., Langmuir, BET, Freundlich, and Sips). The Sips isotherm showed the best overall agreement with the experimental results and the sorption parameters provided estimates of the sorbent surface area (12.0–331 m²/g) and the sorption capacity (Q_m = 0.359–2.20 mmol/g at pH = 4.6; Q_m = 0.070–0.191 mmol/g at pH = 10.3) for the microsphere copolymer/PNP systems in aqueous solution. The nitrogen adsorption properties of the microporous copolymers in the solid state were obtained at 77K with BET surface areas ranging from 0.275 to 4.47 m²/g. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Polyisobutylene based thermoplastic elastomers: VI. Poly(α-methylstyrene-b-isobutylene-b-α-methylstyrene) triblock copolymers by coupling of living poly (α-methylstyrene-b-isobutylene) diblock copolymers

Summary Poly(α-methylstyrene-b-isobutylene-b-α-methylstyrene) (PαMeSt-PIB-PαMePSt) triblock copolymers have been prepared via coupling of living diblock copolymers in a one pot procedure. The PαMeSt-PIB diblock copolymers were synthesized by living sequential cationic polymerization in methylcyclohexane (MeChx)/methylchloride (MeCl) solvent mixtures at −80 °C using BCl₃ for αMeSt polymerization and TiCl₄ for IB polymerization as coinitiators. The crossover efficiency, however, was only ∼57 %, due to intermolecular alkylation (indanyl ring formation) after the addition of TiCl₄. By modifying the PαMeSt end with a short segment of p-chloro-α-methylstyrene before IB addition the crossover efficiency was increased to 90 %. Coupling of the living block copolymers with 2,2-bis[4-(1-phenylethenyl)phenyl]propane (BDPEP) was rapid and gave ∼ 90 % efficiency. Received: 13 July 2000/Accepted: 3 August 2000     

Thermal properties of di- and triblock copolymers of poly(l-lactide) with poly(oxyethylene) or poly(ε-caprolactone)

High molecular weight di- and triblock copolymers of poly(l-lactide), PLLA, (80 wt%) with a crystallizable flexible second component such as poly(ε-caprolactone), PCL, or poly(oxyethylene), PEO, (20 wt%) were obtained in nearly quantitative yields by ring opening of l-lactide initiated by PCL or PEO hydroxy terminated macromers. The copolymers were characterized by ¹H NMR and FTIR spectroscopy and size exclusion chromatography and showed unimodal and narrow molecular weight distributions. X-ray diffraction measurements revealed high crystallinity (38-56%) of the PLLA blocks and gave no clear evidences of PCL or PEO crystallinity. DMTA and DSC techniques showed a melting behaviour of the copolymers (T_m=174-175 °C; ΔH_m=19-37 J/g) quite similar to that of PLLA. PCL and PLLA segments are immiscible, while PLLA and PEO segments are partially miscible in the amorphous phase. Stress-strain measurements indicated a ductile behaviour of the copolymers, characterized by lower tensile moduli (225-961 Pa) and higher elongations at break (25-134%) with respect to PLLA.     

Synthesis of graft copolymers of poly(methacrylic acid)-g-poly(ɛ-caprolactone) by coupling ROP and RAFT polymerizations

The aim of this study was to synthesize graft copolymers of poly(methacrylic acid)-g-poly(?-caprolactone) by a two-step process. In a first part, a macromonomer of 2-hydroxyethylmethacrylate-poly(?-caprolactone) (HEMA-PCL) was synthesized by coordinated anionic Ring Opening Polymerization (ROP). Then graft copolymers were obtained via Reversible Addition Fragmentation chain Transfer (RAFT) copolymerization of HEMA-PCL macromonomer and methacrylic acid (MAA).This two-step synthesis is a really interesting way to adjust and control parameters such as graft density, polymerization degree, copolymer composition, graft length, in order to adapt the final graft copolymers to their future applications. The efficiency of such copolymers in dispersing calcium carbonate into an unsaturated polyester resin has been point out by viscosity measurements.     

Preparation of polystyrene poly(β-hydroxy nonanoate) graft copolymers

Summary Poly(-hydroxy nonanoate)-polystyrene graft copolymers were prepared by the reaction of active polystyrene containing peroxide group with poly(-hydroxy nonanoate) at 80°C. Graft copolymers with a wide graft composition range depending on the amount of active polystyrene in the original mixture were produced and separated from the grafting product by fractional precipitation. NMR and IR spectra of the graft copolymers were containing the characteristic bands of the corresponding blocks. DSC curves of the graft copolymers had a large endotherm between 50 and 110°C.This work was financially supported by KTU research fund and partly supported by TUBITAK Marmara Research Center.     

Synthesis of poly(lactic acid)–poly(ethylene glycol) copolymers using multi-SO3H-functionalized ionic liquid as the efficient and reusable catalyst

Poly(lactic acid)–poly(ethylene glycol) copolymers were synthesized under the catalysis of multi-SO₃H-functionalized ionic liquid. Compared to the ordinary ionic liquids and the traditional Lewis acid catalysts, the ionic liquids with multi-sulfonic acid groups were more catalytically active, and the reaction conversion rate reached up to 97.8 %. The molecular weight of the resulting copolymer was 5.69 × 10⁴ g mol^?1 and the degree of crystallinity was 42.9 %. The copolymers were also of higher hydrophilicity and better mechanical properties. The reaction kinetics of copolymerization was analyzed. The intrinsically high catalytic activity of multi-SO₃H groups originated from the lower activation energy and the higher free acidity. The recovering catalytic activity of the multi-SO₃H ionic liquid catalyst was higher, suggesting that it is a recyclable, environmentally friendly catalyst.     

Magnetite nanoparticles stabilized with polymeric bilayer of poly(ethylene glycol) methyl ether-poly(?-caprolactone) copolymers

In this work, we report a synthetic method of water dispersible magnetite nanoparticles having oleic acid and poly(ethylene glycol) methyl ether-poly(?-caprolactone) (mPEG-PCL) amphiphilic block copolymer as polymeric stabilizers. The particles were prepared by coprecipitation of Fe(II) and Fe(III) in NH₄OH and had bilayer surface with hydrophobic inner layer and hydrophilic corona. mPEG-PCL copolymer was synthesized by a ring-opening polymerization of ?-caprolactone using mPEG as a macroinitiator in the presence of stannous octoate catalyst. FTIR and thermogravimetric analysis (TGA) indicated the presence of the copolymer on the particle surface. Roles of reaction parameters, such as stabilizer concentrations and time of ultrasonicating treatment, on percent of magnetite in the complex and its magnetic properties were investigated. Transmission electron microscopy (TEM) showed the average particle size about 9.0 ± 1.1 nm in diameter. Vibrating sample magnetometry (VSM) measurement indicated that the magnetite nanoparticles were superparamagnetic at room temperature. Approximately 6.8 ± 0.5% of indomethacin model drug (68 μg/mg of magnetite) was effectively entrapped on the particles.     

Synthesis of poly(phenylene oxide) — aromatic polyester multiblock copolymers

Summary Poly(phenylene oxide) (PPO) — aromatic polyester multiblock copolymers were synthesized by polycondensation of bisphenol-A / isophthalic acid or m- and p-hydroxybenzoic acids in the presence of PPO having a carboxylic acid at one end and a phenolic hydroxy group at the other using triphenylphosphine / hexachloroethane as coupling agent. TG analysis showed that the multiblock copolymer showed relatively high thermal stability. Received: 5 January 1998/Accepted: 4 February 1998     

The nucleation effect of N,N′-bis(benzoyl) alkyl diacid dihydrazides on crystallization of biodegradable poly(l-lactic acid)

Five N,N??-bis(benzoyl) alkyl diacid dihydrazides were synthesized from benzoyl hydrazine and alkyl diacyl dichloride which were derived from alkyl diacid via acylation. PLLA/N,N??-bis(benzoyl) alkyl diacid dihydrazide samples were prepared by melt blending and hot-press forming process. The nucleation effect of N,N??-bis(benzoyl) alkyl diacid dihydrazide on crystallization of biodegradable poly(l-lactic acid) (PLLA) was investigated using differential scanning calorimetry (DSC) and vicat softening analysis. The results showed that five N,N??-bis(benzoyl) alkyl diacid dihydrazides acted as powerful nucleating agent for PLLA; with incorporation of N,N??-bis(benzoyl) alkyl diacid dihydrazide, the crystallization peak became sharper and shifted to higher temperature as the degree of supercooling decreased at a cooling rate of 1?°C/min from melt. The nucleation activities of five N,N??-bis(benzoyl) alkyl diacid dihydrazides were quantitatively determined. It is shown that N,N??-bis(benzoyl) suberic acid dihydrazide has higher nucleating activity than the other N,N??-bis(benzoyl) alkyl diacid dihydrazides. In the presence of N,N??-bis(benzoyl) alkyl diacid dihydrazide, the melting behavior of PLLA is affected significantly. In addition, the thermal stability of PLLA/0.8?% N,N??-bis(benzoyl) alkyl diacid dihydrazide is tested and reported. Compared to the neat PLLA, the onset degradation temperature of PLLA/0.8?% N,N??-bis(benzoyl) alkyl diacid dihydrazide samples has been decreased significantly.     

Effect of immobilization of poly(γ-glutamic acid) on the biocompatibility of electrospun poly (L-lactide) mats

In this study, poly(L-lactide) (PLLA) non-woven mats were prepared by electrospinning technique, followed by treating with oxygen plasma and grafting with 3-aminopropyl triethoxysilane (APTES), then immersed in poly(γ-glutamic acid) (γ-PGA) solution to form a layer of γ-PGA on the surface. In so doing, hydrophobic PLLA would become highly hydrophilic. Through characterization of hydrophilicity and biocompatibility, the feasibility of these modified mats for wound dressing was evaluated. The results show that after the grafting of γ-PGA, the swelling ratio increased greatly from 7% for pristine PLLA mat to 321% for γ-PGA-grafted PLLA mat, and the contact angle decreased from 112° to 25°. In vitro cytocompatibility tests against L929 fibroblast show that γ-PGA-grafted PLLA was non-cytotoxic. In addition, the proliferation of fibroblasts was higher on γ-PGA-grafted PLLA than on pristine PLLA.     

The crystallization behavior of poly(ethylene glycol)-poly(ε-caprolactone) diblock copolymers with asymmetric block compositions

Crystallization behavior, structural development and morphology evolution of a series of poly (ethylene glycol)-poly(ε-caprolactone) diblock copolymers (PEG-b-PCL) were investigated via differential scanning calorimetry (DSC), X-ray diffraction (XRD) and atomic force microscopy (AFM). In these copolymers, both blocks were crystallizable and biocompatible. The mutual effects between the PEG and PCL blocks were significant, leading to the obvious block composition dependence of the crystallization behavior and morphology of the PEG-b-PCL copolymers. The relative block length determined which block crystallized first. The temperature-dependent XRD measurements confirmed which block crystallized first from the copolymer during the cooling procedure. Single crystals of the PCL and PEG homopolymers and the PEG-b-PCL copolymers were obtained and observed by AFM. The block (PCL or PEG) crystallized first would determine the crystal morphology. The block crystallized later acted as a solvent, which was advantageous to forming perfect single crystals of the whole block copolymers.     

Preparation,characterization and drug release behavior of poly(acrylic acid–co-2-hydroxyethyl methacrylate-co-2-acrylamido-2-methyl-1-propanesulfonic acid) microgels

In this paper, Poly(acrylic acid-co-2-hydroxyethyl methacrylate-co-2-acrylamido-2–methyl-1–propanesulfonic acid (AAc-HEMA-AMPS) microgels were synthesized by using an inverse suspension polymerization technique. The increase in the AMPS content of the microgels composition caused a large increase in water uptake. The morphology of the microgels was examined by environmental scanning electron microscopy (ESEM). The AMPS containing microgels had a mean particle diameter of 10 μm. The glass transition temperature of the microgels were examined by DSC and found that they show single Tg. Lidocaine (LD) and Methylene blue (MB) were used as model drugs for the investigation of drug release behavior of the microgels. Different drug release patterns were observed, for LD and MB loaded microgels. The release studies showed that some of the basic parameters affecting the drug release behavior of microgels were the specific and non-specific interactions between microgel and drug structure and pH of the dissolution medium. These hydrogels may be potential candidates for pH-sensitive applications.