Synthesis and characterisation of styrene butadiene styrene-g-acrylic acid for potential use in biomedical applications

The work undertaken investigates the mechanical and thermal properties of styrene butadiene styrene (SBS) grafted with acrylic acid (AA) for use as a potential biomedical material. SBS-g-AA was synthesised by UV polymerisation and analytical techniques such as differential scanning calorimetry (DSC), attenuated total reflectance infrared Fourier transform spectrometry (ATR-FTIR), dynamic mechanical thermal analysis (DMTA) and tensile tests were used to characterise the grafted copolymers. From the DSC analysis, the glass transitions of polystyrene (PS) and polybutadiene (PB) domains present in the SBS copolymer were detected at 67 °C and ? 90 °C respectively. ATR-FTIR spectral analysis was used in conjunction with the DSC thermographs to analyse the grafted copolymers. The peak (1711 cm^? 1 ) associated with CO stretching in poly acrylic acid was located at 1725 cm^? 1 on the grafted SBS-g-AA copolymer which confirmed grafting took place. Mechanical testing was carried out to analyse the physical attributes of the grafted copolymers. It was found that a decrease in Young's modulus and stress at break occurred for SBS-g-AA copolymers which were soxhlet extracted using chloroform (washed). It was evident from the DMTA results that the glass transition values for each of the washed grafted samples increased, thus establishing that grafting had occurred onto the various butadiene segments along the SBS backbone. The results showed that the hydrophilic monomer was successfully grafted onto a hydrophobic polymer and the mechanical and thermal properties were in the useful range for biomedical applications.     

Preparation,characterization, and blood compatibility of polylactide-based phospholipid polymer

l-α-glycerophosphorylcholine (GPC) was obtained by hydrolysis of lecithin extracted from eggs. FT-IR and ¹H-NMR analysis indicated a successful preparation of GPC. Polylactide-based phospholipid polymer (PLLA-PC) was synthesized by ring-opening polymerization of l-lactide in the presence of GPC to improve the cell/material interfacial reaction of PLLA for tissue engineering applications. The yield of the reaction strongly depended on the reaction time. Values above 80% were obtained which are much higher than those reported in literature. Copolymers with the largest molecular weights were obtained at 122 °C for 48 h. The properties and biocompatibility of the PLLA-PC copolymers were characterized. Surface rearrangement was detected due to the dynamic molecular motion according to X-ray photoelectron spectroscopy data. Besides, increase in hydrophilicity and decreases in fibrinogen adsorption and platelet adhesion were observed due to the hydrophilic phosphorylcholine moieties in the copolymer.     

Synthesis and self-assembly of tunable thermosensitive chitosan amphiphilic copolymers by click chemistry

Amphiphilic chitosan-graft-P(2-(2-methoxyethoxy)ethyl methacrylate-co-oligo(ethylene glycol) methacrylate) (CS-g-P(MEO₂MA-co-OEGMA)) copolymers were synthesized by the “graft onto” method via click chemistry. The graft copolymers were characterized by ¹H NMR and ATR FT-IR measurements. The self-assembly behavior and tunable thermosensitive properties of CS copolymers in water were investigated by TEM, DLS, and transmittance. The lower critical solution temperature (LCST) values of CS copolymer micelle solutions were tuned by altering the molar ratio of MEO₂MA and OEGMA in copolymers. Furthermore, the copolymer micelles can reversibly swell and shrink in response to external temperature. The obtained tunable thermosensitive amphiphilic CS copolymers have both the unique properties of P(MEO₂MA-co-OEGMA) and chitosan, and will have the potential applications in the biomedical field.     

P(NIPAAm-co-AAPBA-co-HPM-co-TMSPM)四元共聚物的温度及葡萄糖响应行为

通过自由基聚合法将N-异丙基丙烯酰胺(N-isopropylacrylamide,NIPAAm)、3-丙烯酰胺基苯硼酸(3-acrylamidophenylboronic acid,AAPBA)、甲基丙烯酸羟丙酯(Hydroxypropyl methacrylate,HPM)和甲基丙烯酸(3-三甲氧基硅)丙酯(3-trimethoxysilylpropyl methacrylate,TMSPM)合成为P(NIPAAm-co-AAPBA-co-HPM-co-TMSPM)四元共聚物。采用傅里叶变换红外光谱、核磁共振氢谱和动态光散射等手段对终产物进行化学结构、分子组成和响应行为等方面的鉴定与考察。结果表明合成的共聚物由NIPAAm、AAPBA、HPM和TMSPM按照设计的反应物的物质的量比组成,为短链型聚合物,兼具温度和葡萄糖双重响应性能。     

Synthesis, characterization and hydrolytic degradation of degradable poly(butylene terephthalate)/poly(ethylene glycol) (PBT/PEG) copolymers

Hydrolytic degradable PBT/PEG copolymer was synthesized by macromolecular transesterification method from PBT and PEG macromonomers. The resultant copolymers were characterized by ¹H-NMR and GPC. The non-isothermal crystallization behavior of these copolymers was studied by differential scanning calorimetry (DSC). The water absorption and hydrolytic degradation behavior of PBT/PEG copolymers were also studied in detail. This work was partly presented in 6^th ASBM, July 19–22, 2004, Emei City, Chingdu, China. Fan LY is the co-first author for this work.     

Versatile method for synthesis of electrically conductive polypyrrole-polystyrene clay nanocomposites using ATRP and chemical polymerisation methods

A synthetic route for the preparation of a novel solution copolymer derived from styrene (St), pyrrole (Py) and its organoclay nanocomposite with conductive and mechanical properties is demonstrated. The electroactive copolymer of polystyrene-g-polypyrrole (PSt-g-Ppy) nanocomposite was successfully prepared by atom transfer radical polymerisation (ATRP) and chemical polymerisation methods. First, potassium pyrrole was reacted by α-chlorophenyl acetyl chloride to prepare an initiator that can polymerise styrene by ATRP technique. Then, polypyrrole was prepared by chemical polymerisation using FeCl₃ as an oxidant in dichloromethane^,s solvent. Nanocomposites of the copolymer with modified montmorillonite were prepared with a solution intercalation method. The conductivity of the copolymer was measured by the four-point probe method. The structures of the intermediate, copolymer and nanocomposite were investigated by Fourier transform infrared spectroscopy, ¹H-NMR and X-ray diffraction techniques. The molecular weight of the copolymer was determined by gel permeation chromatography. Their thermal behaviour was examined by differential scanning calorimetry and thermogravimetric analyses.     

Acrylic acid–methyl methacrylate copolymer for oral prolonged drug release

Acrylic acid (AA)–methyl methacrylate (MMA) based copolymers, in different molar ratios (3:7, 4:6, 5:5, 6:4, and 7:3) were synthesized using tetrahydrofuran as solvent and AIBN as free radical initiator. Increase in acrylic acid concentration promoted pH-dependent swelling of copolymer and copolymer AA:MMA (3:7) was selected due to minimum swelling. ATR/FTIR and ¹H NMR spectra of the copolymer showed absence of vinyl bond/protons present in the monomers suggesting successful polymerization. The copolymer was hemocompatible. Flurbiprofen sodium microspheres made with the copolymer, by oil/oil solvent evaporation, were spherical, anionic (zeta potential −59.0 mV) and contained 4.53% drug. ATR spectrum of microspheres showed peaks for aromatic C=C stretching and substituted benzene ring, indicating entrapment of flurbiprofen. XRD analysis revealed crystalline structure of flurbiprofen while copolymer and microspheres were amorphous. DSC thermograms showed a sharp melting endotherm of flurbiprofen sodium at 129.26°C against broad endotherms of copolymer and microspheres having peaks at 82.24 and 86.59°C, respectively. The thermogram of microspheres did not show the melting peak of flurbiprofen. The microspheres exhibited no drug release at pH <6.8 and released 83.4 and 99% drug at pH 6.8 and 7.4 in 3 h. The microspheres did not adhere on gastric mucosa at pH 1.2 but showed mucoadhesion time of 28 min on intestinal mucosa at pH 6.8. Thus, the microspheres on oral administration, would release the drug in distal ileum, suggesting the potential of the hemocompatible copolymer for enteric coating for prolonged drug release.     

Investigating of polysulfide and epoxy‐polysulfide copolymer curing

Polysulfide can be cured in various methods. In this work, the effect of various oxidative curing agents (manganese dioxide and para quinonedioxime) in presence of curing accelerator (Diphenylguanidine) on mechanical‐dynamical properties and cure time of polysulfide resin (G4) was investigated. Results showed that mentioned oxidative curing agents have no remarkable effect on mechanical properties and cure time. But preferred method is preparation of polysulfide‐epoxy copolymer. This copolymer is a new class of liquid polymer composition containing block copolymers, with alternating blocks of polysulfide and polyepoxide. in different epoxy/polysulfide ratio, the epoxy‐polysulfide copolymer showd different tensile strenght, elongation, hardness, gel time, viscosity and Tg, but epoxy free polysulfide approximately revealed constant mechanical and dynamical properties so that epoxidized polysulfide had excellent mechanical properties and suitable curring times in comparison with those samples which were cured in other methods. FT‐IR spectroscopy, viscometry and GPC were used to verify the formation of epoxy‐polysulfide copolymer. Results obtained from DMTA and SEM showed that phase separation of epoxy resin from the copolymer matrix took place and The glass transition temperature (Tg) of the cured copolymer was between the cured epoxy and polysulfide glass transition temperatures.     

Characterization of temperature-sensitive membranes prepared from poly(vinylidene fluoride)-graft-poly(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide) copolymers obtained by atom transfer radical polymerization

In this paper, poly(vinylidene fluoride)-graft-poly(N-isopropylacrylamide) (PVDF-g-PNIPAAm) copolymers were synthesized directly via grafting temperature-sensitive material NIPAAm on PVDF by atom transfer radical polymerization (ATRP). The chemical structure of the graft copolymers was characterized by Fourier transform infrared (FTIR) and ¹H-NMR spectroscopy. The temperature-sensitive membranes were prepared from the PVDF-g-PNIPAAm copolymers by the immersion precipitation process of the phase inversion method. The chemical composition and pore structure of the PVDF-g-PNIPAAm membranes were studied by X-ray photoelectron spectroscopy (XPS) and an automatic mercury porosimeter, respectively. The effects of temperature on pure water flux and bovine serum albumen (BSA) rejection ratio of the membranes were also investigated. The results showed that the grafted PNIPAAm chains tended to enrich on the surfaces of the membranes or the membrane pores during the membrane-forming process. Pore diameter and porosity of the copolymer membranes were larger than those of the pristine PVDF membranes. Also, the PVDF-g-PNIPAAm membranes could exhibit temperature-sensitive performance in water flux and BSA rejection measurements.     

Synthesis and characterization of poly(L-lactic acid-co-ethylene oxide-co-aspartic acid) and its interaction with cells

Multiblock terpolymer of poly(L-lactic acid)/ poly(ethylene oxide)/poly(L-aspartic acid), (PLLA/PEO/ PAsp) was synthesized by ring opening polymerization of β -benzyl L-aspartate N-carboxyanhydride, Asp(OBzl)-NCA with α-ω -hydroxy terminated triblock PLLA/PEO/PLLA copolymer. The resulting multiblock terpolymer was characterized by several techniques including Fourier transform infrared spectroscopy and differential scanning calorimetry.¹H nuclear magnetic resonance spectra indicated the molar ratio of PLLA/PEO/PAsp (OBzl) to be 86/10/4. Thermal gravimetric analysis and environmental scanning electron microscopy data showed that PLLA/PEO/PAsp had crystalline and brittle structure. In order to improve its mechanical and physical properties, the terpolymer was blended with high molecular weight poly(L-lactic-co-glycolic acid) copolymer, PLGA(85/15) (M_w: 95000 gmol^{− 1}) in 25/75 and 50/50 mole ratios. The hydrolytical degradation properties of these polymers were studied. Degradation experiments were performed during a 48-day period in pH:7.4 phosphate-buffered saline (PBS) at 37^∘C. The observed molecular weight losses were 91% and 67% for the 25/75 and 50/50 mixtures, respectively. In vitro attachment and growth of L929 mouse fibroblasts on these biopolymers were also investigated. Cell growth experiments indicated that the copolymer blend allowed the attachment and growth of cells.     

Performance enhancement induced by electrospinning of polymer electrolytes based on poly(methyl methacrylate-co-2-acrylamido-2-methylpropanesulfonic acid lithium)

A series of novel fibrous polymer electrolytes with high ionic conductivity based on electrospun poly(methyl methacrylate-co-2-acrylamido-2-methylpropanesulfonic acid lithium) (P(MMA-co-AMPSLi)) membranes were prepared and characterized. P(MMA-co-AMPSLi) was synthesized by free radical copolymerization of MMA and AMPS, followed by ion exchange of the H⁺ with Li⁺. The fibrous polymer electrolytes were fabricated by immersing the electrospun P(MMA-co-AMPSLi) membranes into the liquid electrolyte. Fourier transform infrared spectroscopy and ¹H-nuclear magnetic resonance were used to characterize the structure of the copolymers. Thermogravimetric analysis was applied to investigate the thermal properties of the copolymers. Scanning electromicroscope was employed to observe the morphology of electrospun membranes before and after soaking the liquid electrolyte. AC impedance and linear sweep voltammetry were adopted to measure the electrochemical properties of the fibrous polymer electrolytes. The incorporation of the AMPSLi units effectively improved the electrospinnability of the copolymer, increased the dielectric constants of the electrospun membranes, and enhanced the dimensional stability by maintaining the pore structures even after the membranes absorbing large amounts of liquid electrolytes. As a result, the ionic conductivity of the polymer electrolytes increased with the increase in the molar ratio of AMPSLi units, and the highest ion conductivity was up to 4.12 × 10⁻³ S cm⁻¹ at room temperature. Meanwhile, the polymer electrolytes studied in this work exhibited a sufficient electrochemical stability (up to 5.0 V) that allows the safe operation in lithium-ion batteries.     

Optical properties of polyethylene/styrene-co-methacrylate copolymers IPN-like networks: Effect of different methacrylate styrene co monomers on properties

Low-density Polyethylene (PE) were synthesized with poly[butyl methacrylate (B)-co-styrene (S)], poly(dodecyl methacrylate(D)-co-styrene] and poly(ethyl hexyl methacrylate (EH)-co-styrene] copolymers in order to obtain IPN-like networks. Different S/methacrylate copolymer molar ratios going from 0/100 up to 60/40, a molar percentage of 1.0% of 1,4-butanedioldimethacrylate (b) and 3 wt% of 2,5-dimethyl-2,5-di-(tert-butyl peroxy) hexane (Luperox 101) were used. The samples were analyzed at RT by WAXS, swelling in CCl₄ and mechanical tensile tests. Dynamic-mechanical tests and optical investigations were performed in a temperature range between RT and 180°C. All the IPN types showed optical reversible transitions (transparency-to opacity and vice versa) with varying temperature, due to a refractive index (RI) matching-mismatching of PE and copolymer networks. The copolymer chemical nature as well as its composition affected sensitively most of the analyzed properties.     

带有环氧基团含氟共聚物对环氧涂料的改性

采用自由基乳液聚合的方法制备带有环氧基团的聚丙烯酸全氟烷基乙酯-甲基丙烯酸缩水甘油酯-苯乙烯无规共聚物P(FA-co-GMA-co-St),用红外光谱(FT-IR)和核磁共振(1H-NMR)对共聚物进行表征并将其用于环氧涂料的改性。XPS测试结果表明,带有环氧基团的含氟共聚物改性环氧涂层经蒸馏水浸泡48 h后接触角下降了15°为116°,表面氟元素含量下降了5.36%;而不带有环氧基团共聚物改性环氧漆膜经水浸泡48 h以后接触角下降了48°为88°,表面氟元素含量下降了7.94%。GMA单体的引入极大地提高了环氧涂层在湿润环境中的疏水性。     

Melt-processable acrylonitrile–methyl acrylate copolymers and melt-spun fibers containing MicroPCMs

Acrylonitrile–methyl acrylate (AN–MA molar ratio 85/15) copolymer and copolymers containing 5–25 wt% of microencapsulated phase change materials (MicroPCMs) were synthesized by aqueous redox initiated polymerization. MicroPCMs were incorporated into the copolymer at the step of polymerization. The copolymers were processed by environment friendly, solvent-free melt-spinning. The structures and properties of the copolymers and as-spun fibers containing MicroPCMs were characterized by Nuclear Magnetic Resonance (¹H NMR), Gel Permeation Chromatography (GPC), Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TG), Scanning Electronic Microscope (SEM), X-ray Diffraction (XRD), and Melting Index (MI). The results show that the composition of AN–MA copolymer agrees well with the feeding ratio of AN and MA. The copolymers containing MicroPCMs can be processed at 200 °C. The crystalline enthalpies of the fibers containing 20 and 25 wt% of MicroPCMs are 21 and 25 J/g, respectively; and they increase steadily as the contents of MicroPCMs increase. Tensile strengths of the as-spun fibers are in the range of 1.0–3.2 cN/dtex. The fibers are potentially used as raw materials to fabricate thermo-regulated fabric for comfort clothing.     

Effect of recrystallization and texture on mechanical properties of extruded AA7003 alloy

The microstructure, texture and mechanical properties of AA7003 extrusion sheets processed with different parameters were investigated. Furthermore, the effects of the microstructure and texture on the mechanical properties were discussed. The grain morphology and the texture were analyzed by using a combination of scanning electron microscopy and electron backscatter diffraction. Moreover, the mechanical properties were measured by tensile tests and the tensile fracture morphology was also analyzed by scanning electron microscopy. The results showed that the maximum recrystallization extent occurred at the extrusion process conditions of T = 450 °C and v = 1 mm/s, and the increase in recrystallization extent had a negative effect on the tensile strength. Moreover, a relatively strong recrystallization cube orientation <100> existed when the extrusion temperature was 470 °C, showing a high tensile strength and elongation. Thus, it can be concluded that the cube texture is beneficial to the tensile strength and elongation in extruded AA7003 alloy.     

Characterization of temperature-sensitive membranes prepared from poly(vinylidene fluoride)-graft-poly(N-isopropylacrylamide) copolymers obtained by atom transfer radical polymerization

In this paper, poly(vinylidene fluoride)-graft-poly(N-isopropylacrylamide) (PVDF-g-PNIPAAm) copolymers were synthesized directly via grafting temperature-sensitive material NIPAAm on PVDF by atom transfer radical polymerization (ATRP). The chemical structure of the graft copolymers was characterized by Fourier transform infrared (FTIR) and ¹H-NMR spectroscopy. The temperature-sensitive membranes were prepared from the PVDF-g-PNIPAAm copolymers by the immersion precipitation process of the phase inversion method. The chemical composition and pore structure of the PVDF-g-PNIPAAm membranes were studied by X-ray photoelectron spectroscopy (XPS) and an automatic mercury porosimeter, respectively. The effects of temperature on pure water flux and bovine serum albumen (BSA) rejection ratio of the membranes were also investigated. The results showed that the grafted PNIPAAm chains tended to enrich on the surfaces of the membranes or the membrane pores during the membrane-forming process. Pore diameter and porosity of the copolymer membranes were larger than those of the pristine PVDF membranes. Also, the PVDF-g-PNIPAAm membranes could exhibit temperature-sensitive performance in water flux and BSA rejection measurements.     

Electrochemical copolymerization of dibenzo-18-crown-6 and carbazole and characterization of their copolymer

The electrochemical copolymerization of carbazole (CZ) and dibenzo-18-crown-6 (DBC) was successfully achieved in pure boron trifluoride diethyl etherate (BFEE) by direct anodic oxidation of the monomer mixtures on the platinum or stainless steel electrodes. The optimal feed ratio together with the suitable applied potential for their copolymerization was determined. The copolymer films, which were electrosynthesized with a feed ratio of CZ/DBC = 1:5, owned both the advantages of poly(dibenzo-18-crown-6) (PDBC) and polycarbazole (PCZ), such as nice electrochemical behavior, excellent fluorescence properties and good mechanical properties. Besides, the copolymers possessed better thermal stability and higher electrical conductivity than those of PDBC or PCZ. The structure of the copolymers was investigated by UV–vis and FT-IR spectroscopy. Fluorescent spectral studies revealed that the dedoped copolymer film was a good blue-light emitter with strong emission at 410 nm. With these advantageous properties, as-formed poly(CZ-co-DBC) films may be a good candidate for optoelectronic devices.     

抑制阴离子聚合副反应条件下苯乙烯/丁二烯多嵌段共聚物的反应挤出聚合

基于通过限制正负离子对之间通道尺度,实现抑制阴离子聚合副反应的设想,在反应挤出制备苯乙烯/丁二烯多嵌段共聚物的过程中引入了一种P-配合物,分别采用一次加料法及二次分段加料法合成了两种不同结构的多嵌段共聚物。结果表明,P-配合物对抑制高温阴离子本体聚合中出现的交联副反应有显著效果,且有利于增加共聚物中聚苯乙烯多嵌段的长度。1H-NMR、GPC、TEM及力学性能的测试表明,所得嵌段共聚物中丁二烯含量均在18%以上,其无缺口冲击强度达45 kJ/m2,与KR03树脂相当。样品PSB-2的弯曲强度从后者的34 MPa提高至56 MPa,同时其弯曲模量及拉伸断裂延伸率的提高幅度也均在40%以上。     

Poly(diphenylamine-<Emphasis Type="Italic">co</Emphasis>-aniline) copolymers for supercapacitor electrodes

Polyaniline, polydiphenylamine, and two copolymers with precursor monomers molar ratios of 1:1 and 3:1 (anilinium dodecyl sulfate (P1):diphenylamine) were synthesized via oxidative polymerization in a water/ethanol interfacial system. The morphology characterization and physicochemical properties showed that the copolymers share polyaniline or polydiphenylamine characteristics, depending on the monomer molar ratio. The electroactivity characterization indicated that the polydiphenylamine (PDPA) repeating units provided the copolymers with better cycling stability, whereas PAni repeating units reduced resistance and improved storage capacity, generating a synergistic interaction. Particularly, the copolymer with the highest content of P1, showed a specific capacitance of 341.93 F g^?1, with a 74.5% capacitance retention after 500 cycles, which suggests a feasible application in electrodes for supercapacitor design.     

熔融缩聚合成聚乳酸-聚乙二醇共聚物及其性能研究

采用羧基封端乳酸预聚物与聚乙二醇熔融缩聚合成了聚乳酸-聚乙二醇共聚物,并用GPC、FTIR、1H-NMR等方法表征了预聚物与共聚物,结果表明,预聚物的羧基封端率高于95%,预聚物的相对分子质量可由投料比(物质的量比)控制.热分析结果表明,共聚物中聚乳酸链段呈无规分布,而聚乙二醇链段能够形成结晶微区.力学性能测试结果表明,共聚物的断裂伸长率达371%,有望在聚乳酸韧性改性方面得到应用.