含疏水链节的聚N-异丙基丙烯酰胺共聚物的温敏性

采用溶液聚合法合成了一系列N-异丙基丙烯酰胺(NIPAM)与甲基丙烯酸甲酯、丙烯酸乙酯、丙烯酸丁酯或甲基丙烯酸丁酯的无规共聚物,用浊度观测法和光散射法测定了不同共聚物水溶液的温敏相转变行为.结果表明:所得共聚物的低临界溶解温度(LCST)均低于均聚物PNIPAM的,酯类单体的结构和含量对共聚物的LCST有显著影响,其中酯基上的烷基对共聚物LCST的影响能力大于丙烯酸酯α位上的烷基,前者对增大共聚物的疏水性有更大贡献.通过NIPAM与特定丙烯酸酯单体进行无规共聚可以合成转变温度低于PNIPAM均聚物且具有预设LCST数值的水溶性温敏聚合物.     

温度敏感聚(N-异丙基丙烯酰胺-co-甲基丙烯酰氧乙基二甲基辛基溴化铵)水凝胶的溶胀性能研究

由于改变亲水／疏水单体比值、与离子单体共聚心、改变凝胶内部结构等均可不同程度地调整温敏水凝胶的溶胀性能,本研究选择一种既含疏水烷基又含季铵盐正离子型亲水基团的两亲性单体——甲基丙烯酰氧乙基二甲基辛基溴化铵（ADMOAB）,结构如示意图1所示．与N-异丙基丙烯酰胺（NIPAM）聚合,制备了P（NIPAM-co-ADMOAB）共聚水凝胶,以便在引入离子型结构单元的同时,改变凝胶体系中亲水／疏水单体比值,避免单纯增加疏水单体引起的水凝胶溶胀性降低问题,并考察了ADMOAB对水凝胶溶胀性能的影响,对该类水凝胶迄今鲜见相关文献报道．该研究对进一步了解水凝胶的构效关系、探索有效控制溶胀性能的途径具有积极意义．     

丙烯酸β-羟丙酯/乙烯基吡咯烷酮水凝胶的合成和热敏行为的研究

用自由基共聚法合成了一系列 β -羟丙酯 ( β -HPAT)和乙烯基吡咯烷酮 (NVP)的共聚物及其水凝胶。发现共聚物的水溶液有敏锐的温敏行为 ,最低汇溶温度 (LCST)随NVP含量的增加而升高 ,随着反应单体总浓度的增加 ,相变敏锐性下降且LCST也随之下降。通过考察水凝胶的溶胀率 (SR) ,发现共聚凝胶在适当的单体浓度 ,交联剂浓度和较宽的单体浓度配比范围内 ,有较灵敏的温敏行为。     

N-异丙基丙烯酰胺/丙烯酸胆甾醇酯共聚物研究

合成和表征了N 异丙基丙烯酰胺 (NIPAM)与丙烯酸胆甾醇酯 (CHA)的共聚物 .利用表面张力和荧光探针法研究了共聚物水溶液的表面活性性能 ,确定了其临界胶束浓度 (CMC) .利用浊度法和荧光探针法测定了共聚物的最低临界溶液温度 (LCST) .研究发现 ,在聚N 异丙基丙烯酰胺 (PNIPAM)分子链中引入疏水结构单元CHA会使其LCST下降 ;且随着共聚物中CHA含量的增加 ,LCST下降幅度增加 .在PNIPAM链段中引入少量的CHA就会使其表现出明显的两亲性 ,共聚物在水中能形成有壳核结构的稳定胶束 .通过将疏水化合物胆甾醇作为模拟药物包埋在胶束的疏水核中的研究 ,证实所得的胶束能包埋疏水药物 ,且随着包埋胆甾醇含量的增加 ,胶束平均粒径增大 .     

聚(N,N′-二乙基丙烯酰胺)水凝胶的制备及其溶胀动力学

以N,N′-二乙基丙烯酰胺(DEA)为单体,偶氮二异丁腈(AIBN)为引发剂,分别采用疏水性的1,2-二乙烯苯(DVB)和水溶性的N,N′-亚甲基双丙烯酰胺(BIS)为交联剂制备了温度敏感水凝胶聚(N,N′-二乙基丙烯酰胺)(PDEA).制得的PDEA水凝胶的低临界溶解温度(LCST)在30 ℃附近,初步讨论了交联剂的用量和性质对水凝胶性能的影响.并对其在不同温度下达到溶胀平衡时的溶胀比,去溶胀动力学及干凝胶的再溶胀动力学过程进行了研究.     

温度/pH敏感性接枝共聚物水凝胶P(DMAEMA-g-NIPAM)的 合成及性质研究

利用大分子单体技术, 采用自由基溶液聚合合成了温度/pH敏感性聚甲基丙烯酸-N,N-二甲氨基乙酯接枝聚N-异丙基丙烯酰胺[P(DMAEMA-g-NIPAM)]水凝胶. 用红外光谱及扫描电镜对凝胶的组成及形貌进行了表征. 凝胶的去溶胀和溶胀动力学研究表明, 所合成的凝胶具有温度和pH敏感性. 与传统的聚丙烯酸系水凝胶相比, P(DMAEMA-g- NIPAM)具有相反的pH敏感性; P(DMAEMA-g-NIPAM)凝胶在55 ℃时具有较快的去溶胀速率, 随着凝胶中接枝链PNIPAM量的增加, 凝胶的去溶胀速率加快.     

体积相转变温度可调的温敏性N-异丙基丙烯酰胺共聚物微凝胶的制备与性能研究

选用甲基丙烯酸异丙酯(iPMA)与N-异丙基丙烯酰胺(NIPAM)共聚,制备了一系列疏水改性、相转变温度可调的温敏性P(NIPAM-co-iPMA)微凝胶.利用透射电子显微技术(TEM)、浊度法、动态光散射(DLS)技术及示差扫描量热(DSC)技术对所得微凝胶的形态及去溶胀行为进行了表征.TEM与DLS结果表明,所制备的微凝胶具有规则的球型形态.浊度、DLS及DSC结果表明,疏水性单体iPMA的引入能有效调节共聚物微凝胶的相转变温度;在所考察的范围内,微凝胶的相转变温度随iPMA投料比的增加几乎呈线性降低.     

荧光探针法对N-异丙基丙烯酰胺-丙烯酰胺共聚物水溶液相变的研究

合成了多种不同配比的N 异丙基丙烯酰胺 (NIPAM )与丙烯酰胺 (AM )的共聚物 .用荧光探针法研究了共聚物溶液荧光光谱随温度升高而引起的变化 .研究表明 :共聚物的最低临界溶液温度 (LCST)取决于AM与NIPAM的组成比 .AM的比例越大 .LCST就越高 ,且有较好的正比关系 .通过以共价键连接于共聚物的荧光探针法 (标记法 )和以小分子探针混入共聚物水溶液的方法 (混入法 )测定上述体系LCST的结果比较 ,发现标记探针法具有较高的灵敏度 ,更适宜用来研究共聚物水相体系的相变问题 .     

海藻酸钠和聚N-异丙基丙烯酰胺半互穿网络水凝胶的溶胀动力学研究

以海藻酸钠 (SA)和N 异丙基丙烯酰胺 (NIPAM)为原料 ,制备出具有温度敏感性的半互穿网络水凝胶 (SA PNIPAMsemi IPN) .主要研究了海藻酸钠用量、水介质温度及pH值对该凝胶溶胀速率的影响 .结果表明 ,在PNIPAM最低临界溶解温度 (LCST)以下 ,该凝胶的溶胀速率随着凝胶网络中SA组分的增加而增大 ,且溶胀速率取决于高分子链的松弛速率 ;pH对凝胶溶胀速率的影响与温度有关 ,温度对溶胀速率的影响与pH有关 .     

手性温敏凝胶Poly(NIPAM-co-AAc-L-Trp)的制备及性能

利用L-色氨酸(L-Trp)为手性源,经酯化、缩合等反应制备手性单体AAc-L-Trp,进而在交联剂N,N’-亚甲基双丙烯酰胺(MBAA)和引发剂偶氮二异丁腈(AIBN)的作用下,与N-异丙基丙烯酰胺(NIPAM)发生自由基共聚制备了一种可用于手性拆分的新型手性温敏水凝胶Poly(NIPAM-co-AAc-L-Trp),其结构经IR确证.通过对其温敏性研究发现,相比于PNIPAM凝胶,疏水性手性单体的引入使Poly(NIPAM-co-AAc-L-Trp)凝胶的温敏性下降,LCST随着手性单体含量的增加而降低.以DL-苯丙氨酸为模型药物对其手性识别和拆分性能进行研究,结果表明,手性温敏凝胶可选择性地吸附D-型对映体,且吸附量随着手性单体含量增加而增加;提高温度(45°C)有利于手性温敏凝胶对DL-苯丙氨酸的拆分.     

NIPAM共聚物多孔水凝胶的光引发RAFT合成及其溶胀性能

采用光引发可逆加成-断裂链转移(RAFT)方法,在室温下先合成了链端含有三硫代碳酸酯基的大分子链转移剂聚(N,N'-二甲基丙烯酰胺)(PDMAM),然后与N-异丙基丙烯酰胺(NIPAM)、N,N'-二甲基双丙烯酰胺(BIS)交联共聚合,并通过聚乙二醇的制孔作用制得PNIPAM-g-PDMAM梳型/多孔水凝胶.采用FTI...     

Synthesis of the Functional Hydrogels: Poly(N-isopropylacrylamide) Threaded onto the PEG Backbones Via RAFT

Functional poly(N-isopropylacrylamide) (PNIPAM) hydrogels were prepared by reversible addition fragmentation chain transfer (RAFT) polymerization of NIPAM in the presence of four-arm poly(ethylene glycol) (4A-PEG) as backbone and 4-cyanopentanoic acid dithiobenzoate functional α -cyclodextrin threaded onto the PEG as chain transfer reagent (CTA).The structure of the hydrogels was characterized in detail with FTIR techniques. The analytical results demonstrated that α -cyclodextrin remains in as-obtained hydrogels. The swelling behavior was investigated and the functional hydrogels (functional gels) showed accelerated shrinking kinetics and higher swelling ratio comparing with conventional hydrogel (CG). It could be attributed to the presence of dangling chains. The hydrogel exhibited rapid swelling and deswelling kinetics. In principle, the hydrogel might find a number of applications including an on-off system and drug delivery systems.     

Synthesis and characterization of thermoresponsive poly(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide-co-<Emphasis Type="Italic">N</Emphasis>-hydroxymethylacrylamide-co-2-hydroxyethyl methacrylate) hydrogels

Thermoresponsive hydrogels based on N-isopropylacrylamide, N-hydroxymethylacrylamide, and 2-hydroxyethyl methacrylate, poly(NIPAM–co-NHMAAm–co-HEMA), have been synthesized and their swelling—deswelling behavior studied as a function of NIPAM concentration, NIPAM/NHMAAm and NIPAM/HEMA mole ratio, and total monomer concentration. Copolymers varying in composition have been obtained by redox copolymerization of these three monomers. Temperature has been changed in the ranges from 4 to 70 °C at fixed pH and total ionic strength. Equilibrium swelling ratio, dynamic swelling ratio, and dynamic deswelling ratio were evaluated for all hydrogel systems. The equilibrium swelling ratios of the copolymeric gels decrease with increasing NHMAAm and HEMA content. The formation of the intermolecular hydrogen bonding between hydroxyl and amido groups decreases the hydrophilic group numbers of the gel and the affinity of the gel towards water decreases. The copolymer gels also showed rapid volume transitions with time. The time required for equilibrium shrinking increased with increasing NHMAAm and HEMA content in the gel.     

Synthesis and characterization of thermoresponsive isopropylacrylamide-acrylamide hydrogels

In this study, hydrogels of poly(N-isopropylacrylamide-co-acrylamide) having a thermoresponsive character were prepared by a redox polymerization method. NIPAM-co-AAm hydrogels with different thermoresponsive properties were obtained by changing the initial NIPAM/AAm mole ratio and crosslinker concentration.Equilibrium-swelling ratio, dynamic swelling ratio and dynamic deswelling ratio were evaluated for all hydrogel systems. The fast shrinking was observed with all gels. The time required for equilibrium shrinking increased with the increase of acrylamide content in the gel.     

RADIATION SYNTHESIS AND CHARACTERIZATION OF POLY(AA-co-NVP)/CLAY HYDROGELS

The pH-sensitive P(AA-co-NVP)/clay hydrogels were prepared with the monomers of acrylic acid(AA)and N-vinyl-2-pyrrolidone(NVP)based onγ-ray irradiation technique.The influence of pH values of buffer solutions and contents of clay and NVP on the equilibrium swelling ratio(SR)and compressive properties of the hydrogels was investigated in detail.The results of swelling property tests showed that,with the increase of clay content,the SR of hydrogels increases in the same buffer solution,and the SR of hydrog...     

Chemically Crosslinked pH- and Temperature-Sensitive (N-isopropylacrylamide-co-1-vinyl-2-pyrrolidone) Based on New Crosslinker: I. Swelling Behavior

Novel pH- and temperature-sensitive polymer matrices based on N-isopropylacrylamide have been developed. The hydrogels were prepared by bulk radical polymerization of N-isopropylacrylamide and 1-vinyl-2-pyrrolidinone in appropriate amounts of distilled water using different mol% of traditional N,N-methylene bisacrylamide (MBA) and the new synthesized N,N,N-tris acryloyl melamine (MAAm) crosslinkers. Lower critical solution transition temperatures (LCST) were measured by differential scanning calorimetry. The synthesized hydrogels have LCST lower than 40°C. The influence of environmental conditions such as temperature and pH on the swelling behavior of these polymeric gels was investigated. The swelling behaviors of the resulting gels show pH sensitivity. The crosslinked NIPAAm/VP with MAAm hydrogels exhibited more rapid deswelling rate than NIPAAm/VP hydrogels crosslinked with MBA in pure water in response to abrupt temperature changes from 20°C to 50°C.     

THERMAL-SENSITIVE BETA-CYCLODEXTRIN-CONTAINED POLY(N-ISOPROPYLACRYLAMIDE) HYDROGELS CROSS-LINKED BY Si―O―Si BONDS

A series of novel p（N-isopropylacrylamide） （PNIPAM） hydrogels were synthesized by radical copolymerization of N-isopropylacrylamide （NIPAM） and 3-methacryloxypropyltrimethoxysilane （MPTMS）. The copolymers were then crosslinked through hydrolysis of the siloxane in acetic acid/water mixed solvent. Beta-cyclodextrin （Beta-CD） was introduced into the polymeric networks by condensation of 3-glycidoxypropyltrimethoxysilane derived beta-cyclodextrin （KH560-beta-CD） with MPTMS under acidic condition. These gels were heterogeneous, porous and exhibited fast deswelling kinetics when the temperature was elevated to above lower critical solution temperature （LCST）. The swelling ratios of the gels containing beta-CD at room temperature were higher than that of the normal PNIPAM hydrogel, which was caused by the lower crosslinking density in beta-CD contained gels. In comparison to that of the normal PNIPAM gel, the amount of loaded-drug in the hydrogel containing beta-CD was higher, and the release time of 5-fluorouracil （5-Fu） was prolonged, which was attributed to the formation of inclusion compounds between 5-Fu and beta-CD in gel network.     

THERMAL-SENSITIVE BETA-CYCLODEXTRIN-CONTAINING POLY(N-ISOPROPYLACRYLAMIDE) HYDROGELS CROSSLINKED BY Si-O-Si BONDS -SYNTHESIS, CHARACTERIZATION AND PROLONGING IN VITRO RELEASE OF 5-FLUOROURACIL

A series of novel p(N-isopropylacrylamide) (PNIPAM) hydrogels were synthesized by radical copolymerization of N-isopropylacrylamide (NIPAM) and 3-methacryloxypropyltrimethoxysilane (MPTMS). The copolymers were then crosslinked through hydrolysis of the siloxane in acetic acid/water mixed solvent. Beta-cyclodextrin (Beta-CD) was introduced into the polymeric networks by condensation of 3-glycidoxypropyltrimethoxysilane derived beta-cyclodextrin (KH560-beta-CD) with MPTMS under acidic condition. These gels were heterogeneous, porous and exhibited fast deswelling kinetics when the temperature was elevated to above lower critical solution temperature (LCST). The swelling ratios of the gels containing beta-CD at room temperature were higher than that of the normal PNIPAM hydrogel, which was caused by the lower crosslinking density in beta-CD contained gels. In comparison to that of the normal PNIPAM gel, the amount of loaded-drug in the hydrogel containing beta-CD was higher, and the release time of 5-fluorouracil (5-Fu) was prolonged, which was attributed to the formation of inclusion compounds between 5-Fu and beta-CD in gel network.