Miscibility of block copolymers of poly(ε‐caprolactone) and poly(ethylene glycol) with poly(3‐hydroxybutyrate) as well as the compatibilizing effect of these copolymers in blends of poly(ε‐caprolactone) and poly(3‐hydroxybutyrate)

Atactic poly(3‐hydroxybutyrate) (a‐PHB) and block copolymers of poly(ethylene glycol) (PEG) with poly(ε‐caprolactone) (PCL‐b‐PEG) were synthesized through anionic polymerization and coordination polymerization, respectively. As demonstrated by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) measurements, both chemosynthesized a‐PHB and biosynthesized isotactic PHB (i‐PHB) are miscible with the PEG segment phase of PCL‐b‐PEGs. However, there is no evidence showing miscibility between both PHBs and the PCL segment phase of the copolymer even though PCL has been block‐copolymerized with PEG. Based on these results, PCL‐b‐PEG was added, as a compatibilizer, to both the PCL/a‐PHB blends and the PCL i‐PHB blends. The blend films were obtained through the evaporation of chloroform solutions of mixed components. Excitingly, the improvement in mechanical properties of PCL/PHB blends was achieved as anticipated initially upon the addition of PCL‐b‐PEG. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2600–2608, 2001     

Biodegradable blends of high molecular weight poly(ethylene oxide) with poly(3‐hydroxypropionic acid) and poly(3‐hydroxybutyric acid): a miscibility study by DSC,DMTA and NMR spectroscopy

The miscibility of high molecular weight poly(ethylene oxide) blends with poly(3‐hydroxypropionic acid) and poly(3‐hydroxybutyric acid) (P(3HB)) has been investigated by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) and high‐resolution solid state ¹³C nuclear magnetic resonance (NMR). The DSC thermal behaviour of the blends revealed that the binary blends of poly(ethylene oxide)/poly(3‐hydroxypropionic acid) (OP blends) were miscible over the whole composition range while the miscibility of poly(ethylene oxide)/poly(3‐hydroxybutyric acid) blends (OB blends) was dependent on the blend composition. OB blends were found to be partly miscible at the middle P(3HB) contents (25 %, 50 %) and miscible at other P(3HB) contents (10 %, 75 % and 90 %). Single‐phase behaviour for OP blends and phase separation behaviour for OB blends were observed from DMTA. The results from NMR spectroscopy revealed that the two components in the OP50 blend were intimately mixed on a scale of about 35 nm, while the domain sizes in the OB blend with a P(3HB) content of 50 % were larger than about 32 nm. © 2000 Society of Chemical Industry     

Synthesis and properties of novel biodegradable poly(ε‐caprolactone)/ poly(ethylene glycol)‐based polyurethane elastomers

Elastomeric polyurethanes with tunable biodegradation properties and suitable for numerous biomedical applications were synthesized via reaction of epoxy‐terminated polyurethanes (EUPs) with 1,6‐hexamethylenediamine as curing agent. The EUPs themselves were prepared from glycidol and isocyanate‐terminated polyurethanes made from poly(ε‐caprolactone) (PCL) or poly(ethylene glycol) (PEG) and 1,6‐hexamethylene diisocyanate. All the polymers were characterized by conventional methods, and their physical, mechanical, thermal, and degradation properties were studied. The results showed that the degradation rate and mechanical properties of the final products can be controlled by the amount of PEG or PCL present in the EUP. Increasing the PEG content causes an increase of hydrolytic degradation rate, and increasing the PCL content improves the mechanical properties of the final products. Evaluation of cytotoxcicity showed nontoxic behavior of the prepared samples, but the cytocompatibility of these polymers needs to be improved. Copyright © 2006 Society of Chemical Industry     

Addition of α‐tocopherol on poly(lactic acid): Thermal,mechanical, and sorption properties

This work investigates the effect of the addition of a well‐known antioxidant, α‐tocopherol in poly (lactic acid) flexural and barrier properties. For that purpose, films of poly(lactic acid) enriched with 0, 2.2, and 4.4% of α‐tocopherol were prepared. Differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical analysis were used to characterize the changes in the mechanical and thermal properties. The sorption of oxygen and carbon dioxide in the prepared enriched films of poly(lactic acid) was measured at different temperatures between 283 and 313 K and pressures up to atmospheric pressure using a Quartz Crystal Microbalance. Although no significant changes were found in the mechanical and thermal properties, the addition of α‐tocopherol promotes an increasing in the oxygen sorption and the convex shape of the isotherms indicate a strong interaction gas‐polymer. Regarding the sorption of carbon dioxide, no pronounced effect was found. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Swelling behaviour of poly(α‐hydroxyacrylic acid) gel

Poly(α‐hydroxy acrylic acid) (PHA) and poly(acrylicacid) (PAA) gels were prepared by irradiating the respective 15 wt% aqueous solutions with γ‐rays. Swelling ratios for PHA gel were measured as a function of pH and divalent cation (Mg²⁺, Ca²⁺, Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺) concentration C₂ in the external solution to provide a comparison with the results for PAA gels. It was found that the swelling ratio of PHA gel steeply increases between pH 2 and 4, followed by a gradual swelling in the higher pH region. The corresponding steep swelling of PAA gel was observed at pH 3–6. Cation specificity in the equilibrium swelling ratio at a lower C₂ value (1.0 × 10⁻³ M) was approximately consistent with the binding selectivity in the solution system. Typically, the swelling ratio of PHA gel in the presence of Ca²⁺ was significantly lower than in the Mg²⁺ system, while the difference was slight for PAA gel. The response of the swelling ratio to changes in pH and C₂ was analysed as a first order relaxation to estimate the time constants. The (de)swelling kinetics measured by both the pH and C₂ jump were qualitatively interpreted in terms of main‐chain stiffness and intermolecular hydrogen bonding in the respective polymers. © 2000 Society of Chemical Industry     

Characterization and comparison of diblock and triblock amphiphilic copolymers of poly(δ‐valerolactone)

Three types of pegylated amphiphilic copolymers of poly(δ‐valerolactone) (PVL) were copolymerized with methoxy poly(ethylene glycol) (MePEG) and poly(ethylene glycol) (PEG₄₀₀₀ and PEG_10,000), respectively. Pegylation of PVL allowed copolymers possessing amphiphilic property and efficiently self‐assembled to form micelles with a low critical micelle concentration (CMC) in the range of 10^?7–10^?8M. The average molecular weight of copolymers was in the range of 10,000–20,000 Da, and the polydispersity of copolymers was about 1.7–1.8. Higher mobility of low molecular weight PEG (i.e., MePEG and PEG₄₀₀₀) than high molecular weight PEG_10,000 allowed valerolactone ring opening more efficient in terms of PVL/MePEG and PVL/PEG₄₀₀₀ copolymers possessing longer chain length in hydrophobic domain. Pegylated PVL with low CMC and triblock structure was preferred to encapsulate drug during micelle formation. Although all of these amphiphilic copolymers exhibited controlled release character, the micelles formed by triblock copolymer possessed a more stable core‐shell conformation than that by diblock copolymer, and resulted in the release of drug from triblock micelles slower than that from diblock micelles. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1836–1841, 2006     

Synthesis and characterization of copolymers based on poly(butylene terephthalate) and ethylene oxide‐poly(dimethylsiloxane)‐ethylene oxide

A series of thermoplastic elastomers based on ethylene oxide‐poly(dimethylsiloxane)‐ethylene oxide (EO‐PDMS‐EO), as the soft segment, and poly(butylene terephthalate) (PBT), as the hard segment, were synthesized by catalyzed two‐step, melt transesterification reaction of dimethyl terephthalate (DMT) with 1,4‐butanediol (BD) and α,ω‐dihydroxy‐(EO‐PDMS‐EO). Copolymers with a content of hard PBT segments between 40 and 90 mass % and a constant length of the soft EO‐PDMS‐EO segments were prepared. The siloxane prepolymer with hydrophilic terminal EO units was used to improve the miscibility between the polar comonomers, DMT and BD, and the nonpolar PDMS. The molecular structure and composition of the copolymers were determined by ¹H‐NMR spectroscopy, whereas the effectiveness of the incorporation of α,ω‐dihydroxy‐(EO‐PDMS‐EO) into the copolymer chains was verified by chloroform extraction. The effects of the structure and composition of the copolymers on the melting temperatures and the degree of crystallinity, as well as on the thermal degradation stability and some rheological properties, were studied. It was demonstrated that the degree of crystallinity, the melting and crystallization temperatures of the copolymers increased with increasing mass fraction of the PBT segments. The thermal stability of the copolymers was lower than that of PBT homopolymer, because of the presence of thermoliable ether bonds in the soft segments. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Studies on aluminum-isopropoxide doped poly(ethylene oxide), poly(vinyl alcohol), and poly(ethylene oxide)-poly(vinyl alcohol) blends

Poly(ethylene oxide), poly(vinyl alcohol), and their blend in a 40 : 60 mole ratio were doped with aluminum isopropoxide. Their structural, thermal, and electrical properties were studied. Aluminum isopropoxide acts as a Lewis acid and thus significantly influences the electrical properties of the polymers and the blend. It also acts as a scavanger for the trace quantities of water present in them, thereby reducing the magnitude of proton transport. It also affects the structure of polymers that manifests in the thermal transformation and decomposition characteristics. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2147–2157, 1998     

Poly(γ-glutamic acid) hydrogel prepared from microbial poly(γ-glutamic acid) and alkanediamine with water-soluble carbodiimide

Poly(γ-glutamic acid) (PGA) hydrogels have been prepared from microbial PGA produced by Bacillus subtilis F-02-1, water-soluble carbodiimide (WSC), and alkanediamines such as 1,3-propanediamine (1,3-PD), 1,4-butanediamine (1,4-BD), and 1,6-hexanediamine (1,6-HD) in aqueous medium. The carboxyl groups of PGA were activated by the addition of WSC in deionized water, and the PGA-WSC adduct was produced. PGA hydrogels could be produced after the mixing of PGA-WSC and alkanediamine in deionized water. This alkanediamine to which both amino groups reacted with the carboxyl groups of PGA plays the role of a crosslinking point. When the amount of PGA was 100 mg, WSC was 50 mg or more, and 1,3-PD was 25 μL or more in 2 mL of deionized water, PGA hydrogels could be produced. Specific water contents (weight of absorbed water/weight of dry gel) ranged from 300 to 1,993 g/g in the case of 1,3-PD. If the PGA-WSC adduct was freeze-dried, the yield of the PGA hydrogel became higher than that when PGA-WSC was not freeze-dried. The highest yield of the PGA hydrogel from 100 mg of PGA, 100 mg of WSC, and 100 μL of 1,3-PD in 2 mL of deionized water using the freeze-dry method was 39.9 mg of dry PGA hydrogel with a 650 g/g specific water content. The order of yield was 1,6-HD > 1,4-BD > 1,3-PD from 100 mg of PGA-100 mg of WSC in 2 mL of deionized water. The order of the specific water content was 1,3-PD (462 g/g) > 1,4-BD (234 g/g) > 1,6-HD (199 g/g). This order may be due to the higher reaction probability between the activated carboxyl groups in the PGA-WSC and both amino groups in the alkanediamine with longer methylene chains, indicating that the crosslinking density of the PGA hydrogel is higher and the specific water content is lower. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 1889–1896, 1997     

Synthesis and characterization of poly(ε‐caprolactone)‐b‐poly(ethylene glycol)‐b‐poly(ε‐caprolactone) triblock copolymers with dibutylmagnesium as catalyst

Two series of poly(ε‐caprolactone)‐b‐poly(ethylene glycol)‐b‐poly(ε‐caprolactone) triblock copolymers were prepared by the ring opening polymerization of ε‐caprolactone in the presence of poly(ethylene glycol) and dibutylmagnesium in 1,4‐dioxane solution at 70°C. The triblock structure and molecular weight of the copolymers were analyzed and confirmed by ¹H NMR, ¹³C NMR, FTIR, and gel permeation chromatography. The crystallization and thermal properties of the copolymers were investigated by wide‐angle X‐ray diffraction (WAXD) and differential scanning calorimetry (DSC). The results illustrated that the crystallization and melting behaviors of the copolymers were depended on the copolymer composition and the relative length of each block in copolymers. Crystallization exothermal peaks (T_c) and melting endothermic peaks (T_m) of PEG block were significantly influenced by the relative length of PCL blocks, due to the hindrance of the lateral PCL blocks. With increasing of the length of PCL blocks, the diffraction and the melting peak of PEG block disappeared gradually in the WAXD patterns and DSC curves, respectively. In contrast, the crystallization of PCL blocks was not suppressed by the middle PEG block. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Hydrolytic degradation of poly(oxyethylene)–poly-(ε-caprolactone) multiblock copolymers

The degradation of poly(oxyethylene)–poly(ε-caprolactone) (POE–PCL) multiblock copolymers was investigated at 37°C in a 0.13M, pH 7.4 phosphate buffer selected to mimic in vivo conditions. The copolymers were obtained by coupling polycaprolactone diols and poly(ethylene glycol) diacids using dicyclohexylcarbodiimide as coupling agent. Various techniques, such as weighing, size exclusion chromatography, infrared, ¹H nuclear magnetic resonance, differential scanning calorimetry, and X-ray diffractometry, were used to monitor changes in total mass, water absorption, molar mass, thermal properties, degree of crystallinity, and composition. The results showed that introduction of POE sequences considerably increased the hydrophilicity of the copolymers as compared with PCL homopolymers. Nevertheless, the degradability of PCL sequences was not enhanced due to the phase separation between the two components. Significant morphological changes were also observed during the degradation. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 989–998, 1998     

Synthesis,characterization, and hydrolytic degradation of biodegradable poly(ether ester)‐urethane copolymers based on ε‐caprolactone and poly(ethylene glycol)

In this article, a new kind of biodegradable poly(ε‐caprolactone)‐poly(ethylene glycol)‐poly(ε‐caprolactone)‐based polyurethane (PCEC‐U) copolymers were successfully synthesized by melt‐polycondensation method from ε‐caprolactone (ε‐CL), poly(ethylene glycol) (PEG), 1,4‐butanediol (BD), and isophorone diisocyanate (IPDI). The obtained copolymers were characterized by ¹H‐nuclear magnetic resonance (¹H‐NMR), FTIR, and gel permeation chromatography (GPC). Thermal properties of PCEC‐U copolymers were studied by DSC and TGA/DTG under nitrogen atmosphere. Water absorption and hydrolytic degradation behavior of these copolymers were also investigated. Hydrolytic degradation behavior was studied by weight loss method. ¹H‐NMR and GPC were also used to characterize the hydrolytic degradation behavior of PCEC‐U copolymers. The molecular weight of PCL block and PEG block in soft segment and the content of hard segment strongly affected the water absorption and hydrolytic degradation behavior of PCEC‐U copolymers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and properties of poly(ethylene oxide) star polymers

Poly(ethylene oxide) (PEO) star polymers were prepared by anionic polymerization of methacryloyl chloride and glyceryl trimethacrylate with sec‐butyllithium in cyclohexane. The ensuing polymers were grafted with poly(ethylene glycol) of molecular weight 400. The final product was washed with methylene chloride and analyzed with infrared spectroscopy, differential scanning calorimetry, and thermogravimetry. Star polymers of PEO were also prepared by anionic polymerization of glycidol with sec‐butyllithium in cyclohexane. The initiator was chosen so as to yield a polymer of 10,000 molecular weight. The resulting polymers were analyzed by nuclear magnetic resonance, infrared spectroscopy, and thermogravimetry. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 322–327, 2003     

Biodegradable and photocurable multiblock copolymers with shape‐memory properties from poly(ε‐caprolactone) diol,poly(ethylene glycol), and 5‐cinnamoyloxyisophthalic acid

Biodegradable and photocurable multiblock copolymers of various compositions were synthesized by the high‐temperature solution polycondensation of poly(ε‐caprolactone) (PCL) diols of molecular weight (M_n) = 3000 and poly(ethylene glycol)s (PEG) of M_n = 3000 with a dichloride of 5‐cinnamoyloxyisophthalic acid (ICA) as a chain extender, followed by irradiation by a 400 W high‐pressure mercury lamp (λ > 280 nm) to form a network structure. The gel contents increased with photocuring time, reaching a level of over 90% after 10 min for all copolymers without a photoinitiator. The thermal and mechanical properties of the photocured copolymers were examined by DSC and tensile tests. In cyclic thermomechanical tensile tests, the photocured ICA/PCL/PEG copolymer films showed good shape‐memory properties at 37–60°C, with both shape fixity ratio and shape recovery ratio over 90% at a maximum tensile strain of 100–300%. The water absorption of these copolymers and their rate of degradation in a phosphate buffer solution (pH 7.0) at 37°C increased significantly with increasing PEG content. The novel photocured ICA/PCL/PEG multiblock copolymers are potentially useful in biomedical applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Interface formation of Ca with poly(p-phenylene α,α′-diphenyl vinylene) and poly(p-phenylene α-phenyl vinylene)

We have investigated the interface formation of Ca with poly(p-phenylene α,α′-diphenyl vinylene) (PPV-DP) and poly(p-phenylene α-phenyl vinylene) (PPV-P) using X-ray photoemission spectroscopy (XPS). Similarly to our earlier findings in metal/PPV interface formation, the O 1s peak shifted toward a lower binding energy as soon as Ca was deposited on to the polymers. This was accompanied by the formation of Ca? O, suggesting a chemical origin for the O 1s shift. By contrast, the C 1s peak shift toward a lower binding energy was observed relatively later, after about 4 Å of Ca deposition. At the same time, a new C 1s component became noticable at about ?1.5 eV relative to the initial C 1s peak. This component signifies the possibility of polymer disruption by the Ca atoms to form Ca? C species. The C 1s peak shift is attributed to Ca induced surface band bending and barrier formation as in the case of metal/PPV interface formation. The disruption of the polymer may also induce changes in the interface electronic states and contribute to the C 1s peak shift. From the intensity attenuation analysis, we conclude that the initial 15 Å of Ca overlayer is contaminated by the Ca? O and Ca? C species and the overlayer is pure beyond 15 Å of Ca coverage.     

Porous biodegradable polyester blends of poly(L‐lactic acid) and poly(ε‐caprolactone): physical properties,morphology, and biodegradation

Poly(L ‐lactic acid) (PLLA), poly(ε‐caprolactone) (PCL), and their films without or blended with 50 wt% poly(ethylene glycol) (PEG) were prepared by solution casting. Porous films were obtained by water‐extraction of PEG from solution‐cast phase‐separated PLLA‐blend‐PCL‐blend‐PEG films. The effects of PLLA/PCL ratio on the morphology of the porous films and the effects of PLLA/PCL ratio and pores on the physical properties and biodegradability of the films were investigated. The pore size of the blend films decreased with increasing PLLA/PCL ratio. Polymer blending and pore formation gave biodegradable PLLA‐blend‐PCL materials with a wide variety of tensile properties with Young's modulus in the range of 0.07–1.4 GPa and elongation at break in the range 3–380%. Pore formation markedly increased the PLLA crystallinity of porous films, except for low PLLA/PCL ratio. Polymer blending as well as pore formation enhanced the enzymatic degradation of biodegradable polyester blends. Copyright © 2006 Society of Chemical Industry     

Multifunctional gentamicin supplementation of poly(γ‐glutamic acid)‐based hydrogels for wound dressing application

The process of wound healing is composed of coagulation, inflammation, fibroplasia, collagenation, epithelization, and wound contraction. The wound dressing should protect the wound from bacterial infection, maintain a moist healing environment, and promote cell migration to reconstruct damaged tissue, and be easy to apply and remove to improve patient comfort. The purpose of our study was to develop multifunctional hydrogels composed of genipin‐crosslinked biodegradable biomaterials of poly(γ‐glutamic acid) and gelatin, encapsulating gentamicin to accelerate wound healing. The results of swelling ratio measurements clearly indicate that hydrogel composition of poly(γ‐glutamic acid)–gelatin had a higher swelling ratio and lower peel adhesion properties than gelatin hydrogel alone. In an in vitro study, the gentamicin incorporated in prepared hydrogels effectively inhibited target microorganisms and produced a higher expression of Type I collagen in fibroblast cells. Confocal laser scanning microscopy revealed that the fibroblast cells cultured in the hydrogel membranes produced fibroblast cell migration and showed a continuous lined cytoskeletal distributing status. In the in vivo study, it was found that the gentamicin incorporated in genipin‐crosslinked γ‐PGA–gelatin wound dressing demonstrates the potential of such biologically functionalized dressing to accelerate wound closure and, hence, its potential clinical usefulness. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

生物医用材料聚L-乳酸的生物相容性及降解性能研究

通过DSC、SEM、TGA等分析手段对合成得到的聚L-乳酸(PLLA)进行了细胞种植、动物体内包埋及热降解实验,其生物相容性及体内、体外降解情况。实验证明PLLA材料具有良好的生物相容性和组织相容性。用其薄膜埋植于兔子皮下,兔子的生存状态及生长良好;其薄膜可为细胞在其表面上生长、增殖、分泌基质提供良好的微环境。PLLA材料分子量越大降解速度越慢,且体内降解的速度要比体外降解的速度快。     

Synthesis and characteristics of a novel aliphatic polycarbonate,poly[(propylene oxide)‐co‐(carbon dioxide)‐co‐(γ‐butyrolactone)]

A novel aliphatic polycarbonate, poly[(propylene oxide)‐co‐(carbon dioxide)‐co‐(γ‐butyrolactone)] [P(PO? CO₂? GBL)], was synthesized by the copolymerization of carbon dioxide, propylene oxide (PO) and γ‐butyrolactone (GBL). The resulting copolymers were determined by FTIR and NMR spectral analysis with viscosity‐average molecular weights (M_v) from 50 000 to 120 000 g mol^?1. According to elemental analysis, the calculated data of elemental contents in P(PO? CO₂? GBL)44 were close to the found data. The result showed that GBL was inserted into the backbone of poly[(propylene oxide)‐co‐(carbon dioxide)] successfully. GBL offered an ester structural unit that gave the copolymer better degradability. The correlations between reaction conditions and properties were studied. When GBL content increased, the M_v and the glass transition temperature (T_g) of the copolymers improved relative to an identical copolymer without GBL. Prolonging the reaction time of the copolymerization resulted in increases in M_v and T_g. P(PO? CO₂? GBL) exhibited a high T_g above 40 °C. The rate of backbone degradation increased with increasing GBL content. Copyright © 2005 Society of Chemical Industry     

Synthesis and characterization of poly(methylphenylsilylene)–poly(ethylene oxide) and poly(methylphenylsilylene)–polyisoprene multiblock copolymers

Multiblock copolymers were synthesized through condensation reactions of end‐groups of α,ω‐dichloro‐poly(methylphenylsilylene) with hydroxyl end‐groups of poly(ethylene glycol) or the chain‐ends of ‘living’ polyisoprenyl disodium. Optimum conditions have been sought through kinetic studies and by investigation of model reactions. The overall molecular weight distribution of poly(methylphenylsilylene)‐block‐poly(ethylene oxide) is characterized in terms of Flory's theory of condensation reactions, while the limiting step in the reaction is tentatively attributed to the formation of aggregates. © 2001 Society of Chemical Industry