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。     

皮肤敷料用温敏性氮异丙基丙烯酰胺接枝改性聚四氟乙烯膜

采用紫外辐照法将N-异丙基丙烯酰胺(NIPAAm)接枝于聚四氟乙烯(PTFE)膜表面,得到聚氮异丙基丙烯酰胺接枝改性PTFE膜(PTFE-gPNIPAAm)。采用SEM和IR,对接枝前后PTFE膜的形貌结构及成分进行表征分析,计算其接枝率和透湿率,并考察其在不同温度下的溶胀性能。结果表明,通过紫外辐照,PNIPAAm接枝于PTFE膜表面;当NIPAAm单体浓度为5%(质量分数)时,接枝率最高;PTFE膜的透湿率在接枝后显著降低;PTFE-gPNIPAAm膜的溶胀行为在32℃附近发生明显变化。该接枝改性多孔膜有望用作具有温敏特性的易剥离皮肤伤口敷料。     

聚偏氟乙烯微孔膜一步法亲水化改性研究

采用高能电子束预辐照接枝的方法,研究了液相丙烯酸(AAc)和苯乙烯磺酸钠(SSS)双元混合体系对聚偏氟乙烯(PVDF)微孔膜的接枝改性,用一步法直接制备了含有羧酸基团和磺酸基团的强亲水性PVDF微孔膜.考察了辐照剂量、反应时间、反应温度、单体浓度、单体配比以及反应溶液pH值等对接枝率的影响.采用FT-IR、接触角和水通量表征改性前后的膜表面性质和膜性能.结果表明,接枝改性后膜的亲水性增强,接触角随接枝率的增加而降低,水通量随接枝率的增加呈现出先升后降的变化,这主要是由于高接枝率时膜表面和膜孔被接枝链堵塞.     

聚两性电解质修饰聚偏氟乙烯膜的制备及抗污染性能

膜污染是膜分离技术广泛应用的瓶颈之一。文中通过自由基接枝聚合法将2-丙烯酰胺基-2-甲基丙磺酸(AMPS)和甲基丙烯酰氧乙基三甲基氯化铵(DMC)接枝到聚偏氟乙烯(PVDF)膜上构建聚两性电解质化膜表面。研究了改性前后膜表面结构和抗污染性能的变化。随着单体投料量增加,聚两性电解质的接枝率逐渐增加;接枝聚两性电解质后,膜亲水性逐渐增强,膜表面孔尺寸减小。与纯PVDF膜相比,改性膜具有较低的蛋白质吸附量;在牛血清蛋白(BSA)溶液渗透过程中,膜的不可逆污染向可逆污染转化。由于可逆污染可通过简单的纯水清洗得到抑制,改性膜具有较高的通量恢复率。这个结果证明了聚两性电解质的引入赋予PVDF膜良好的抗污染性能。     

聚偏氟乙烯接枝改性膜的抗污染性能研究

通过紫外辐射引发原子转移自由基聚合的方法制备了接枝率不同的聚偏氟乙烯接枝甲基丙烯酸甲酯膜(PVDF-g-PMMA),通过对牛血清蛋白(BSA)的过滤来检验膜的抗污染性能。结果显示,随着膜的MMA接枝率增加,膜的亲水性增加,对BSA的静态吸附量减少。接枝率为23.5%的PVDF-g-PMMA膜的吸附量为PVDF膜吸附量的1/2。膜自身阻力Rm和浓差极化边界层阻力Rc的和占总过滤阻力的78%以上,是导致亲水性接枝膜的膜通量降低的主要因素。随着膜接枝率的增加,Rm和Rc逐渐减小,且整个膜过滤阻力逐渐减小。     

异丙基丙烯酰胺接枝改性聚氨酯多孔膜及其理化性能研究

采用紫外辐照法将N-异丙基丙烯酰胺(NIPAAm)接枝于聚氨酯(PU)膜表面,得到聚氮异丙基丙烯酰胺接枝改性PU膜(PU-g-PNIPAAm)。采用SEM和IR对接枝前后PU膜的形貌结构及成分进行表征分析,计算其接枝率和透湿率,并考察其在不同温度下的溶胀性能。结果表明,PNIPAAm通过紫外辐照成功接枝于PU膜表面;当NIPAAm单体浓度为5%(质量分数)时,接枝率最高;PU膜的透湿率在接枝后显著降低,更接近于人体皮肤;PU-g-PNIPAAm膜在32℃附近发生明显的溶胀行为变化。该接枝改性多孔膜有望用作人工皮肤的表皮材料。     

温敏功能棉纤维:过硫酸铵引发棉接枝聚N-异丙基丙烯酰胺

选用过硫酸铵APS作为引发剂,水作为溶剂,通过沉淀自由基接枝聚合引发棉纤维接枝PNIPAAm。红外分析和电镜观察均表明棉已成功接枝上PNIPAAm,获得了棉纤维接枝PNIPAAm共聚物(接枝棉);采用质量法计算接枝棉的接枝率,并研究了单体和引发剂浓度对接枝率的影响;MDSC测试表明接枝棉在PNIPAAm的LCST附近(33℃)显示了温敏性,且对应的可逆焓变随接枝率的增大而增大。通过测量不同环境温度下水滴在接枝棉表面的接触角表征接枝棉的温敏亲/疏水性,并研究了接枝率对接枝棉的温敏亲/疏水性影响。通过滴水试验(AATCC 79-2000标准)测量不同环境温度下水滴完全浸入接枝棉的浸润时间表征了接枝棉的温敏吸水性。该接枝体系组成简单,操作容易,所选水溶剂对环境无污染、环保。     

P(NIPAAm-PEGMA)接枝聚丙烯多孔膜表面的抗污染及自清洁性能

以等离子体引发方法制备了聚(N-异丙基丙烯酰胺-聚乙二醇甲基丙烯酸酯)(P(NIPAAm-PEGMA))接枝的聚丙烯(PP)多孔膜。考察了改性膜水通量及表面润湿的温敏性质,并研究了其表面抗牛血清白蛋白(BSA)污染及自清洁性能。结果表明,聚乙二醇(PEG)侧链引入后,P(NIPAAm-PEGMA)保留了体积相转变性质,并在低临界溶解温度(LCST)上下均能展现良好的表面亲水性。得益于表面亲水性的改善,改性膜在过滤BSA溶液时的通量衰减率降低至18.8%。经简单的变温水清洗,BSA污染膜的水通量恢复率可达98.2%,且表面甚少污染物残留。P(NIPAAm-PEGMA)接枝链的亲水性及体积相转变是实现改性膜表面自清洁的原因。     

两性荷电纳滤膜的研究

通过紫外辐照接枝法在酚酞基聚芳醚酮(PEK-C)超滤膜表面依次接枝苯乙烯磺酸钠(SSS)和甲基丙烯酰氧乙基三甲基氯化铵(DMC)制成了一种亲水性、表面载有两种不同电荷的纳滤膜.通过测定膜对不同盐溶液表观截留率的变化,系统研究了单体浓度、接枝时间对膜分离性能的影响.结果表明,采用该方法制成的亲水性两性纳滤膜对高价正负离子...     

接枝层厚度对聚(N-异丙基丙烯酰胺)改性表面与蛋白质相互作用的影响

采用表面引发原子转移自由基聚合(ATRP)的方法制备了聚(N-异丙基丙烯酰胺)(PNIPAAm)改性表面,通过改变聚合时间进而调控表面接枝层厚度.水接触角和蛋白质吸附测试发现PNIPAAm改性表面的浸润性和对蛋白质吸附都具有一定的温度响应性,且随着PNIPAAm接枝层厚度的增加,该温度响应性有一定程度的增强.同时,纤维蛋白原和溶菌酶的吸附测试表明PNIPAAm改性表面对尺寸不同的蛋白质具有不同的温度响应性.     

Surface modification of polystyrene and poly(ethylene terephtalate) by grafting poly(N-isopropylacrylamide)

In this work, poly(N-isopropylacrylamide) (PNIPAAm) was incorporated into previously oxidized PS and PET surfaces by grafting using two photo-initiation pathways. The incorporation of PNIPAAm was observed by drop water contact angle measurements, dyeing with Methylene Blue and AFM images analysis of the virgin and modified polymers. It was verified that the grafting process depends on the chemical surface environment. The grafted surfaces are hydrophilic below 32 °C and hydrophobic above this temperature. The transition is due to the incorporated PNIPAAm. This characteristic gives to the grafted materials potential to be applied as biomaterials.     

聚羟基乙酸接枝淀粉共聚物的合成和性能

以乙交酯和淀粉为原料,三乙胺为催化剂,在二甲基亚砜介质中合成了聚羟基乙酸接枝淀粉共聚物。讨论了原料配比和反应时间对共聚物接枝率(G)、接枝效率(E)和单体转化率(C)的影响。采用核磁共振谱仪(1H-NM R)、傅立叶变换红外光谱仪(FT-IR)、X射线粉末(多晶)衍射仪(XRD)、差式扫描量热仪(DSC)以及体外降解试验,研究了接枝共聚物的结构和性能。实验结果表明,将乙交酯单体和淀粉接枝共聚,可以得到一类新的可降解聚合物。     

聚氯乙烯接枝聚乳酸的合成及生物降解性

以环己酮为溶剂,将聚氯乙烯(PVC)与聚乳酸(PLA)的钠盐进行反应,合成了以PVC为主链、PLA为支链的接枝聚合物(PVC-g-PLA)。讨论了实验条件对产物接枝率的影响,用核磁共振氢谱(1H-NM R)、红外光谱(FT-IR)和凝胶渗透色谱(GPC)对接枝聚合物进行了表征。采用土壤掩埋试验和扫描电镜(SEM)分析的方法,研究了接枝物的生物降解性。     

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.     

Preparation of poly(N-isopropylacrylamide) brush grafted silica particles via surface-initiated atom transfer radical polymerization used for aqueous chromatography

Thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm) brushes were densely grafted onto silica surface via surface-initiated atom transfer radical polymerization (SI-ATRP). The grafting reaction started from the surfaces of 2-bromoisobutyrate-functionalized silica particles in 2-propanol aqueous solution at ambient temperature using CuCl/CuCl₂/N,N,N′,N′,N″-pentamethyldiethylenetriamine (PMDETA) as the catalytic system. Based on thermogravimetric analysis (TGA) results, the grafting amount and grafting density of PNIPAM chains on the surface of silica were calculated to be 1.29 mg/m² and 0.0215 chains/nm², respectively. The gel permeation chromatography (GPC) result showed the relatively narrow molecular weight distribution (M_w/M_n=1.21) of the grafted PNIPAAm. The modified silica particles were applied as high-performance liquid chromatography (HPLC) packing materials to successfully separate three aromatic compounds using water as mobile phase by changing column temperature. Temperature-dependent hydrophilic/hydrophobic property alteration of PNIPAAm brushes grafted on silica particles was determined with chromatographic interaction between stationary phase and analytes. Retention time was prolonged and resolution was improved with increasing temperature. Baseline separation with high resolution at relatively low temperatures was observed, demonstrating dense PNIPAAm brushes were grafted on silica surfaces.     

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.     

聚乙烯醇接枝聚异丁烯马来酸酐的合成及自组装

主要研究了以聚乙烯醇(PVA)为主链,聚异丁烯马来酸酐(PIBSA)为支链的两亲性接枝共聚物的制备及在溶液中的自组装行为.接枝共聚物由PIBSA和PVA1799通过酯化反应得到,改变投料比能得到不同接枝率的共聚物.以二甲基亚砜(DMSO)做共溶剂,水做选择性溶剂,室温下自组装得到了稳定的聚集体溶液.扫描电镜和透射电镜观...     

Thermosensitive Y-shaped micelles of poly(oleic acid-Y-N-isopropylacrylamide) for drug delivery

A novel thermosensitive amphiphilic copolymer comprised of two hydrophobic poly(oleic acid) (POA) segments and one hydrophilic poly(N-isopropylacrylamide) (PNIPAAm) segment was designed and synthesized. The structure of the copolymer was confirmed as Y-shaped by FTIR, 1H NMR, and SEC-MALLS analysis. A cytotoxicity study shows that the P(OA-Y-NIPAAm) copolymer exhibits good biocompatibility. The copolymer may self-assemble into micelles in water, with the hydrophobic POA segments at the cores of micelles and the hydrophilic PNIPAAm segments as the outer shells. The resulting micelles demonstrate temperature sensitivity with a lower critical solution temperature (LCST) of 31.5 degrees C and a critical micelle concentration (CMC) of 12.6 mg L(-1). Transmission electron microscopy (TEM) shows that the micelles exhibit a nanospheric morphology within a narrow size range of approximately 10-30 nm. A study of controlled release reveals that the self-assembled micelles have great potential as drug carriers.     

Properties and drug release profile of poly(N-isopropylacrylamide) microgels functionalized with maleic anhydride and alginate

This study highlights the advantages of functionalized poly(N-isopropylacrylamide) (PNIPAAm) microgels over pure PNIPAAm microgels in terms of polymer network properties and drug release profiles. PNIPAAm network was modified by addition of maleic anhydride (MA) as a comonomer and by formation of interpenetrating polymer network in the presence of alginate. The functionalized thermosensitive microgels in the size range from 20 to 80 μm and with better performance in comparison with pure PNIPAAm microgels were prepared by inverse suspension polymerization. The impact of MA and alginate on the PNIPAAm microgel structure was evaluated through analysis of microgel size, size distribution, volume phase transition temperature (VPTT), equilibrium swelling ratio as well as morphology of the system. It was shown that the controlled modification of PNIPAAm network could result in microgels of considerably improved swelling capacity with unchanged thermosensitivity and maintained open pore morphology. In addition, drug release behavior of microgels could be markedly altered. Release of procaine hydrochloride from the selected microgels was studied using Franz diffusion cell at temperatures below and above VPTT of the microgels. Temperature-controlled drug release pattern was dependent on the type of functionalization of PNIPAAm network. According to drug loading properties and drug release mechanism, PNIPAAm/MA copolymer microgels demonstrated the optimal performances.