纳米纤维素晶接枝丙烯酸钠共混改性聚醚砜超滤膜的研究

通过ATRP法在纳米纤维素晶(CNCs)上接枝丙烯酸钠(AANa)制备具有pH响应性的晶体粒子,利用红外光谱(FT-IR),X射线光电子能谱(XPS)对接枝前后的CNCs进行分析表征。接枝后的CNCs与聚醚砜(PES)进行共混,通过相转化法制得共混膜,利用扫描电镜(SEM),水通量测试对共混膜进行分析。结果表明,当CNCs-g-AANa添加量为1%时,CNCs-g-AANa/PES共混膜水通量有明显提高;且共混膜具有pH响应性,当pH值7.2时,共混膜水通量为137.47L/(m2·h),相比纯PES膜提高了41%;当pH值下降为3.3时,共混膜的水通量达到218.54L/(m2·h),相比纯PES膜提高124%。     

水性丙烯酸酯共聚物/淀粉共混膜增容剂

以淀粉-g-聚(丙烯酸丁酯-co-丙烯酸)为增容剂,通过共混来改善水性丙烯酸酯共聚物与淀粉共混膜的力学性能,评价了增容剂接枝支链的结构与共混膜力学特性的内在联系,以确定这种增容剂所应具备的分子结构。结果表明,淀粉-g-聚(丙烯酸丁酯-co-丙烯酸)能明显改善共混膜的力学性能,当接枝单体丙烯酸丁酯与丙烯酸的摩尔比为80:20,增容剂用量为丙烯酸酯共聚物和淀粉总量的10%时,共混膜的力学性能最好。     

辐射接枝制备温度敏感PVDF膜性能研究

本文通过预辐照接枝法和共辐照接枝法合成出了具有聚偏氟乙烯(PVDF)骨架和聚N-异甲基丙烯酰胺(PNIPAAm)支链的双亲接枝共聚物。将合成的PVDF-g-PNIPAAm共聚物与PVDF进行溶液共混,通过浸没沉淀相转化法制备共混膜。结果表明,两种方法制备出的共混膜均表现出明显的温度敏感性能,接枝均匀程度的不同明显反映在膜截留率和膜的表面亲水性上。     

pH值敏感响应膜的制备和性能研究

研究了两步光接枝法制备pH敏感响应分离膜的过程中接枝率随实验条件的变化及其对响应性的影响.实验以聚丙烯为基膜、丙烯酸(AA)为接枝单体,用水作溶剂,考察了光引发剂二苯甲酮(BP)的浓度、丙烯酸的浓度以及反应时间对接枝率的影响,采用傅氏变换红外光谱和扫描电镜分别对高分子膜的化学成分和膜的形貌进行了表征.研究结果表明,控制接枝率在1%～6%时,接枝膜具有较为显著的pH值响应性;接枝率为3%时,接枝膜的pH值响应系数达2.3,当接枝率大于6%和接枝率小于1%时,膜几乎不具pH值敏感响应性.为获得满意的pH值敏感响应性,必须将其接枝率控制在适当的范围内.     

pH值敏感响应膜的制备和性能研究

研究了两步光接枝法制备pH敏感响应分离膜的过程中接枝率随实验条件的变化及其对响应性的影响。实验以聚丙烯为基膜、丙烯酸（AA）为接枝单体，用水作溶剂，考察了光引发剂二苯甲酮（BP）的浓度、丙烯酸的浓度以及反应时间对接枝率的影响，采用傅氏变换红外光谱和扫描电镜分别对高分子膜的化学成分和膜的形貌进行了表征。研究结果表明，控制接枝率在1％～6％时，接枝膜具有较为显著的pH值响应性；接枝率为3％时，接枝膜的pH值响应系数达2．3，当接枝率大于6％和接枝率小于1％时，膜几乎不具pH值敏感响应性。为获得满意的pH值敏感响应性，必须将其接枝率控制在适当的范围内。     

pH敏感型管式陶瓷复合膜的制备

采用硅烷偶联剂KH-570在乙醇溶剂中以盐酸溶液为催化剂进行水解后对管式ZrO2陶瓷膜进行表面修饰,进一步用化学接枝法将丙烯酸单体接枝到改性ZrO2陶瓷膜上,制备pH敏感型陶瓷复合膜.系统考察了不同偶联反应条件对氧化锆陶瓷膜的硅烷化改性效果的影响;研究了丙烯酸单体浓度对pH敏感膜渗透通量及pH开关系数的影响.通过扫描电镜(SEM)、X射线光电子能谱(XPS)、热重(TG)及水通量测定等对改性前后膜结构和pH敏感性能进行分析.结果表明,在以乙醇为溶剂进行硅烷化改性后,成功引入了碳-碳双键,并将丙烯酸成功接枝在陶瓷膜表面;单体浓度对pH敏感的膜通量及pH开关系数有重要的影响;所制备膜显示了良好的pH敏感性能.     

两亲性共聚物的合成及其共混合金膜的功能化

近年来,研究者们热衷于研究和开发膜除分离物料以外的其它功能特性,例如膜的高亲水性和抗污染性、生物相容性、环境相应性、催化活性、光电功能等。在膜表面接枝功能基团或与带功能基团的聚合物共混是实现聚合物多孔膜功能化的重要方法。两亲性共聚物(包括嵌段、接枝、超支化共聚物等)以其独特的性能而受到广泛的关注,从分子结构设计出发,合成了一系列与特定膜材料具有良好相容性的两亲性共聚物,嵌段两亲性共聚物,两亲性交替共聚物,两亲性超支化共聚物等,并通过共混的方法使膜表面带有功能基团,赋予聚合物膜某些功能特性。     

聚偏氟乙烯膜表面丙烯酸接枝改性研究

采用自由基接枝聚合反应制备了丙烯酸改性的聚偏氟乙烯膜,研究了单体浓度对接枝率的影响,测定了改性后样品的红外光谱、表面接触角、水通量、蛋白吸附等.结果表明,通过自由基接枝聚合,丙烯酸接枝到膜的表面,明显提高膜的亲水性.接枝后膜的水通量也非常明显下降,特别是在高丙烯酸浓度下.改性的膜的通量对溶液的pH值有明确的响应关系,表明接枝链在水中的溶胀对膜的性能有显著的影响.蛋白吸附实验表明,改性后的膜相比未改性膜有较高的吸附量,而且在酸性情况下,膜的吸附量较大,这主要与丙烯酸和蛋白质之间的相互作用有关.     

纳米纤维素晶须双重接枝共聚物对Cu~(2+)的吸附

将丙烯酸和丙烯酰胺接枝到纳米纤维素晶须表面,制备出双重接枝共聚物。通过红外光谱和偏光显微镜分析表征双重接枝共聚物的官能团和液晶性能,研究了其对Cu2+的吸附性能,考察了吸附时间、吸附温度、pH值和初始浓度对吸附性能的影响。实验结果表明,丙烯酸和丙烯酰胺成功接枝到纳米纤维素晶须的表面;Cu2+的加入影响了双重接枝共聚物的液晶织构;在吸附时间为8h,吸附温度为35℃,pH值为6~8时,双重接枝共聚物对Cu2+具有最佳的吸附效果,最大的吸附容量为38.96mmol/g,吸附过程符合Langmuir方程。     

紫外光引发直接接枝丙烯酸制备聚偏氟乙烯pH敏感膜

聚偏氟乙烯铸膜液中添加多乙烯多胺,制备含碳碳双键的聚偏氟乙烯超滤膜;在不除氧和无光引发剂条件下,采用紫外光直接辐射将单体丙烯酸接枝到聚偏氟乙烯膜表面,制备了聚偏氟乙烯pH敏感膜。考察单体丙烯酸浓度、反应时间与接枝率的关系,当丙烯酸质量分数为40%,反应时间20 min时,膜接枝率为26.6%。当接枝率为18.7%时,膜的pH敏感性最为显著。     

淀粉接枝共聚物在淀粉/聚乳酸共混体系中的作用

研究了淀粉／聚乳酸共混体系的相容性，考察了淀粉－聚醋酸乙烯酯和淀粉－聚乳酸接枝共聚物对淀粉／聚乳酸共混体系相容性的影响。发现上述两种接枝共聚物均可有效地增加淀粉与聚乳酸的相容性，从而提高共混体系的耐水性的力学性能。     

Controlled release camptothecin tablets based on pluronic and poly(acrylic acid) copolymer. Effect of fabrication technique on drug stability, tablet structure, and release mode

Poly(ethylene oxide)-b-poly(propylene oxide)-b-(polyethylene oxide)-g-poly(acrylic acid), a graft-comb copolymer of Pluronic 127 and poly(acrylic acid) (Pluronic-PAA), was explored as an excipient for tablet dosage form of camptothecin (CPT). The tablets were prepared by either direct compression of the drug-polymer physical blend, suspension in ethanol followed by evaporation, or compression after kneading and characterized with respect to their physical structures, drug stability, and release behavior. Porosity and water uptake rate were strongly dependent on the fabrication procedure, ranking in the order: direct compression of physical blend > compression after suspension/evaporation in ethanol > compression after kneading. Tablets prepared by compression of physical blends swelled in water with a rapid surface gel layer formation that impeded swelling and disintegration of the tablets core. These tablets were able to sustain the CPT release for a period of time longer than those observed with the tablets made by either suspension/evaporation or kneading, which disintegrated within a few minutes. Despite the tablet disintegration, the CPT release was impeded for at least 6 hr, which was attributed to the ability of the Pluronic-PAA copolymers to form micellar aggregates at the hydrated surface of the particles. Physical mixing did not alter the fraction of CPT being in the pharmaceutically active lactone form, whilst the preparation of the tablets by the other two methods caused a significant reduction in the lactone form content. Tablets prepared from the physical blends demonstrated CPT release rates increasing with the pH due to the PAA ionization leading to the increase in the rate and extent of the tablet swelling. The results obtained demonstrate the potential of the Pluronic-PAA copolymers for the oral administration of chemotherapeutic agents.     

Controlled Release Camptothecin Tablets based on Pluronic and Poly(acrylic acid) Copolymer. Effect of Fabrication Technique on Drug Stability,Tablet Structure,and Release Mode

ABSTRACT

Poly(ethylene oxide)-b-poly(propylene oxide)-b-(polyethylene oxide)-g-poly(acrylic acid), a graft-comb copolymer of Pluronic® 127 and poly(acrylic acid) (Pluronic-PAA), was explored as an excipient for tablet dosage form of camptothecin (CPT). The tablets were prepared by either direct compression of the drug-polymer physical blend, suspension in ethanol followed by evaporation, or compression after kneading and characterized with respect to their physical structures, drug stability, and release behavior. Porosity and water uptake rate were strongly dependent on the fabrication procedure, ranking in the order: direct compression of physical blend > compression after suspension/evaporation in ethanol > compression after kneading. Tablets prepared by compression of physical blends swelled in water with a rapid surface gel layer formation that impeded swelling and disintegration of the tablets core. These tablets were able to sustain the CPT release for a period of time longer than those observed with the tablets made by either suspension/evaporation or kneading, which disintegrated within a few minutes. Despite the tablet disintegration, the CPT release was impeded for at least 6 hr, which was attributed to the ability of the Pluronic-PAA copolymers to form micellar aggregates at the hydrated surface of the particles. Physical mixing did not alter the fraction of CPT being in the pharmaceutically active lactone form, whilst the preparation of the tablets by the other two methods caused a significant reduction in the lactone form content. Tablets prepared from the physical blends demonstrated CPT release rates increasing with the pH due to the PAA ionization leading to the increase in the rate and extent of the tablet swelling. The results obtained demonstrate the potential of the Pluronic-PAA copolymers for the oral administration of chemotherapeutic agents.     

Thermal study on structural changes and phase transition in high-energy electron-irradiated blends of P(VDF–TrFE) copolymers

Thermal study of high-energy electron-irradiation binary blends of ferroelectric P(VDF–TrFE) copolymers has been investigated by X-ray diffraction, differential scanning calorimetry (DSC) and thermally stimulated depolarization current (TSDC). X-ray diffraction shows some degree of mixing inside a crystal lattice due to significant changes in the ferroelectric-to-paraelectric phase transition behavior from all-trans to trans-gauche conformation in nanometer range after irradiation. In DSC thermograms, it is found that both the Curie temperature and melting temperature decrease with the dose and that the F–P transition temperatures and enthalpies of two individual copolymers and the blend merge into one with the increase of dose, indicating that there exists a strong lattice coupling between the two copolymers. The peaks observed in TSDC spectra of the blends exhibit the phase transitional characters of the parent copolymers which demonstrates that the miscibility in the crystalline region for their large compositional discrepancy. The distribution of temperature peaks in TSDC also show that the existence of two types of crystallite in the blend which become more clear after irradiation, confirming the X-ray and DSC results.     

Incorporation of salicylic acid derivatives to hydrophilic copolymer systems with biomedical applications

Hydrogels based on polymeric derivatives of salicylic acid have been prepared for biomedical applications by free radical copolymerization of 2-hydroxy-4-methacrylamidobenzoic acid, 4HMA, and 2-hydroxy-5-methacrylamidobenzoic acid, 5HMA, with 2- hydroxyethylmethacrylate, HEMA, in a wide range of compositions. The reactivity ratios of 4HMA and 5HMA with HEMA in radical copolymerization processes have been determined from their ¹H NMR spectra by applying linearization methods and non-linear least square treatments. Tgs of the corresponding copolymers were analyzed by DSC. The swelling behavior in water of the prepared copolymers was studied in comparison to poly-(HEMA), poly-(4HMA) and poly-(5HMA) hydration degrees, being in all cases superior to 35%. The hydrolytical behavior of the synthesized copolymers was studied at three different pHs (2, 7.4 and 10) determining the release percentage of the salicylic acid derivatives, 4-amino salicylic acid, 4ASA, and 5-amino salicylic acid, 5ASA, analyzed by high performance liquid chromatography (HPLC). The release analysis was followed during 230 days and a pH dependence was observed obtaining the highest release percentages at pH=10, whereas at physiological pH (7.4) the release percentages were in range from 2 to 5% at that time for all copolymer systems. The hydrolytical stability is enough for long-term applications like bone cements, ionomers, etc. © 2001 Kluwer Academic Publishers     

Hydrolytic degradation of PCL/PEO copolymers in alkaline media

PCL/PEO copolymers with different compositions were obtained from ring opening polymerization of -caprolactone in the presence of ethylene oxide and characterized by various analytical techniques. Data collected from DSC and X-ray diffractometry suggested that the copolymer chains possess a blocky structure, leading to both PCL and PEO-type crystalline structures. Hydrolytic degradation of these copolymers was carried out in a pH=10.6 carbonate buffer solution at 37 °C. Comparison was made with a PCL homopolymer and a PCL/PEG blend which had the same gross composition as one of the copolymers. The results showed that the presence of PEO sequences considerably enhanced the hydrophilicity of the copolymers as compared with PCL homopolymer. Nevertheless, the degradability of PCL chains was not enhanced due to the phase separation between the two components. These materials should be of great interest for biomedical uses such as matrices for sustained drug delivery because of the presence of both hydrophilic and hydrophobic microdomains. ©2000 Kluwer Academic Publishers     

TPU/EVM共混体系的动态硫化工艺

比较了通过HAAKE Rheocord90转矩流变仪用两种不同的动态硫化混炼方法对热塑性聚氨酯弹性体/乙烯-醋酸乙烯酯共聚物(TPU/EVM)共混体系性能的影响,硫化剂选用过氧化二异丙苯(DCP);探讨了密炼室转子转速和混炼温度对动态硫化共混物性能的影响。通过相差显微镜和傅立叶变换红外光谱仪(FT-IR)对硫化后共混物的微观结构进一步分析表明:动态硫化后的共混体系力学性能优于未硫化体系;两种不同动态硫化法制备的共混物性能相比,B法优于A法,且B法中两相呈明显互锁结构,相畴较小且均匀;FT-IR表明EVM主链的亚甲基和侧链的甲基参与了交联反应,且主要在亚甲基上;转速为30 r/min和混炼温度为150℃时共混物的综合力学性能最优。     

新型质子交换膜材料及其改性方法研究进展

综述了燃料电池用各种质子交换膜(PEM)材料及其改性方法．PEM材料包括全氟磺酸型离子交换树脂、聚苯并咪唑(PBI)、聚醚醚酮(PEEK)以及各种新型聚合物、嵌段共聚物等，而将这些材料制成PEM所采用的改性方法可分为磺化、酸基络合、杂化、共混、共聚、以及辐射接枝、等离子体等改性处理．还介绍了各种PEM材料的物性特点和PEM材料改性方法及其最新PEM研究报道．     

Acrylic acid–methyl methacrylate (2.5:7.5/2:8) enteric copolymer for colon targeted drug delivery

Enteric copolymers of acrylic acid and methyl methacrylate (2.5:7.5 and 2:8) were prepared using tetrahydrofuran as solvent and AIBN as free radical initiator for colon targeting. FTIR and ¹H NMR spectra of the copolymers showed absence of vinyl bond/protons present in the monomers suggesting successful polymerization. Flurbiprofen sodium microspheres (M1 and M2) made with the copolymers, by oil/oil solvent evaporation, were spherical, anionic (zeta potential –57.8 and –53.7 mV) and contained 5.47 and 5.89% drug. FTIR spectrum of microspheres showed peaks for aromatic C = C stretching and substituted benzene ring, indicating entrapment of flurbiprofen. PXRD 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 copolymers and microspheres. The microspheres released 43 and 36% drug at pH 6.8 in 2 h and 99 and 96% at pH 7.4 in next 3–4 h.The microspheres did not adhere on gastric-mucosa at pH 1.2 but showed mucoadhesion time of 18 min and 9 min on intestinal mucosa at pH 6.8. Thus, the microspheres on oral administration, would release the drug in colon, suggesting the potential of the hemocompatible copolymers for pH dependent colon targeted drug delivery system.     

Bioadhesion of various proteins on random,diblock and triblock copolymer surfaces and the effect of pH conditions

The adhesive interactions of block copolymers composed of poly(methyl methacrylate) (PMMA)/poly(acrylic acid) (PAA) and poly(methyl methacrylate)/poly(2-hydroxyethyl methacrylate) (PHEMA) with the proteins fibronectin, bovine serum albumin and collagen were studied by atomic force microscopy. Adhesion experiments were performed both at physiological pH and at a slightly more acidic condition (pH 6.2) to model polymer–protein interactions under inflammatory or infectious conditions. The PMMA/PAA block copolymers were found to be more sensitive to the buffer environment than PMMA/PHEMA owing to electrostatic interactions between the ionized acrylate groups and the proteins. It was found that random, diblock and triblock copolymers exhibit distinct adhesion profiles although their chemical compositions are identical. This implies that biomaterial nanomorphology can be used to control protein–polymer interactions and potentially cell adhesion.