温敏性微凝胶对蛋白质和酶的吸附性能

用微乳液聚合方法以N-异丙基丙烯酰胺为单体合成了温敏性微凝胶聚N-异丙基丙烯酰胺(PNIPAM),研究了其对两种蛋白质和两种酶的吸附性能,测定了吸附等温线和温度对吸附量的影响。结果表明,微凝胶在低临界溶解温度(LCST)附近吸附蛋白质和酶的量有一突跃,例如在LCST前后,1 g纳米颗粒吸附的酪蛋白的质量分别为225 mg和415 mg;吸附的枯草杆菌蛋白酶的质量分别为12 000U/mg和27 500 U/mg。蛋白质和酶是通过物理吸附作用结合到PNIPAM微凝胶上,可以用调节温度的方法,来控制温敏微凝胶对蛋白质和酶的吸附与脱附。     

温度敏感的固定化纤维素酶的合成及性能

具有低临界溶解温度（LCST）特性的聚合物聚（N-异丙基丙烯酰胺）与纤维素酶键联，对键联后的酶的各种性能进行了研究。实验结果表明，固定化的纤维素酶仍具有LCST特性，其稳定性也有所提高。     

温敏超细颗粒对亲水药物的吸附

用微乳液聚合方法以N 异丙基丙烯酰胺为单体合成了温敏性超细颗粒 ,研究了其对维生素B2 注射液和盐酸普鲁卡因的吸附量随温度的变化 ,结果表明 :在低温 (LCST以下 )下吸附药物 ,而在高温 (LCST以上 )下释放药物。在LCST前后 ,1g超细颗粒吸附的维生素B2 的质量分别为 2 9 59μg和 1 8 1 4μg ,吸附的盐酸普鲁卡因质量分别为 1 1 92 μg和 7 80 μg。聚 N 异丙基丙烯酰胺 (PNIPAM)超细颗粒有可能作为控制药物释放的智能载体。     

温敏性水凝胶的合成及表征

以羟丙基甲基纤维素与丙烯酰氯为原料,制备了羟丙基甲基纤维素丙烯酸酯;以偶氮二异丁腈为引发剂、以羟丙基甲基纤维素丙烯酸酯为大分子交联剂、N-异丙基丙烯酰胺为单体在N,N-二甲基甲酰胺中70℃下通过自由基聚合反应24 h,制备了温度敏感性水凝胶。用DSC对其相转变温度进行了表征,并测定了不同温度下达到溶胀平衡时水凝胶的溶胀比,进行了水凝胶的去溶胀动力学及干凝胶的再溶胀动力学研究。在聚合过程中,加入羟丙基甲基纤维素丙烯酸酯制得的水凝胶:相转变温度由30℃降为29℃;在10℃时溶胀比由29降为24.8;去溶胀速率加快,例如:该水凝胶在10 m in内失水率由56%降为16%,在30 m in内失水率由86%降为19%;并且减慢了凝胶的再溶胀速率。     

热逆变水凝胶及其固定化酶的特性

由Ｎ－异丙基丙烯酰胺及其共聚物合成的水凝胶，当温度升高或降低时，会发生相应的体积收缩或膨胀变化。将酶固定在这种水凝胶中，随着温度的循环变化，它能可逆地开启或关闭酶的活性。本文对热逆变水凝胶固定化天冬酰胺酶的活性随温度的变化进行了研究，发现酶的活性随温度的变化而发生有规律的变化。     

温敏性萃取水凝胶对生物大分子的分离

合成了均聚的聚N 异丙基丙烯酰胺(PNIPAM)水凝胶以及N 异丙基丙烯酰胺与丙烯酰胺共聚的〔P(NIPAM-AM)〕水凝胶,并研究了它们的溶胀性能及其对生物大分子的萃取分离性能。结果表明,两种温敏凝胶具有很好的溶胀性能,其低临界共溶温度(LCST)分别为30 4和31 0℃,它们对蛋白质和酶的分离效率在LCST附近发生突跃,如PNIPAM水凝胶对白蛋白的分离效率在LCST前后从96 2%降至59 8%。当交联剂N,N 次甲基双丙烯酰胺(Bis)的质量分数w(Bis)>4%时,分离效率大于90%(LCST以下)。     

NIPAm-co-Am热敏凝胶LCST的测定

用N-异丙基丙烯酰胺(NIPAm)与丙烯酰胺(Am)共聚得到了NIPAm-co-Am热敏凝胶.通过目测法、吸光光度法、溶胀曲线法和DTA法测定了凝胶的LCST.结果表明目测法简单,但准确度不高;吸光光度法灵敏度高,但对于块状凝胶不适用;溶胀曲线法准确,但操作麻烦,耗时较长;DTA法中人的因素影响较小,但由于水的存在使结果有些偏差.     

AM/NIPAM对P(NIPAM-co-AM)温敏凝胶性能影响

以丙烯酰胺(AM)、N-异丙基丙烯酰胺(NIPAM)为单体,过硫酸铵(APS)-亚硫酸氢钠(SBS)为氧化-还原引发体系,N,N'-亚甲基双丙烯酰胺(BIS)为交联剂,制备了亲水型温敏凝胶P(NIPAM-co-AM)。研究了投料比AM/NIPAM对凝胶性能的影响。结果表明：随着凝胶体系中亲水单体AM比例的增大,共聚凝胶溶胀率、保水率、硬度均提高。当AM从0增大到100%时,凝胶硬度从84.929g增为1255.222g。DSC表明,当AM含量从2%提高到10%时,凝胶LCST从38.61℃增加到57.95℃。随着AM比例降低,凝胶LCST向低温方向移动,相变范围温敏性越好。     

快速响应的温敏性PNIPAAm／粘土复合水凝胶的合成及性能研究

以碳酸钠为制孔剂合成了快速响应的温敏性PNIPAAm／粘土复合水凝胶(NNC水凝胶),DSC分析表明,其体积相转变温度在33℃左右,与传统的PNIPAAm水凝胶没有很大的偏差。动力学研究表明,该水凝胶在温敏膨胀或收缩时,具有快速的响应速率,在5 min内的失水率达90％以上,这与扫描电镜观察到水凝胶具有大而连贯的孔洞结构相一致。     

温度及pH敏感的水凝胶微球合成及其药物缓释研究

采用乳液聚合法,以N-异丙基丙烯酰胺(NIPAM)和丙烯酸(AAc)为功能单体,共聚制备了粒径较为均匀的水凝胶微球.该微球具有温度及pH双重敏感性,其最低临界溶解温度(LCST)随着pH值及AAc含量的不同而改变.此外,还以吡啶硫酮钠(ZNP)为水溶性小分子药物模型,研究了该微球对该药物的负载及控释情况.研究显示,吡啶...     

Synthesis and characterization of radio‐opaque thermosensitive poly[N‐isopropylacrylamide‐2,2′‐(ethylenedioxy)bis(ethylamine)‐2,3,5‐triiodobenzamide]

BACKGROUND: In situ gelling polymers, like poly(N‐isopropylacrylamide) (poly(NIPAAm)), have many potential medical applications due to their biocompatibility and thermosensitivity. RESULTS: Radio‐opaque thermosensitive poly(NIPAAm) grafted with 10.7 wt% 2,2′‐(ethylenedioxy)bis(ethylamine)‐2,3,5‐triiodobenzamide was successfully synthesized and characterized. The conjugated polymer showed good visibility with X‐ray fluoroscopy. The polymer had a lower critical solution temperature of 30 °C after conjugation with triiodobenzamide as determined by cloud point determination and a transition peak temperature of 33.3 ± 0.57 °C as determined by differential scanning calorimetry. CONCLUSION: The polymer synthesized was highly visible under X‐rays, based upon the percentage incorporation of triiodobenzamide. After conjugation of the NIPAAm to the triiodobenzamide through a bis(ethylamine) linkage, the resultant polymer retained lower critical solution temperature characteristics in a temperature region that makes it physiologically useful. Copyright © 2009 Society of Chemical Industry     

Simultaneous lower and upper critical solution temperature‐type co‐nonsolvency behaviour exhibited in water–dioxane mixtures by linear copolymers and hydrogels containing N‐isopropylacrylamide and N,N‐dimethylacrylamide

The co‐nonsolvency behaviour in water–dioxane mixtures of linear copolymers and hydrogels consisting of N‐isopropylacrylamide (NIPAM) and N,N‐dimethylacrylamide (DMAM) was studied as a function of solvent composition and temperature. The composition of the copolymers, P(NIPAM‐co‐DMAMx), in DMAM units, x, varies from x = 0 up to x = 100%. It is shown that the copolymers combine the lower critical solution temperature (LCST)‐type co‐nonsolvency behaviour of poly‐NIPAM with the upper critical solution temperature (UCST)‐type co‐nonsolvency behaviour of poly‐DMAM. Depending on x, both the LCST‐ and UCST‐type co‐nonsolvency behaviour may be simultaneously observed in water‐rich and dioxane‐rich solvent mixtures, respectively. Due to this complex phase separation behaviour, the variation of the reduced viscosity of the linear copolymers, as well as the swelling–deswelling behaviour of the respective hydrogels, are shown to be temperature‐ and solvent‐sensitive. Copyright © 2006 Society of Chemical Industry     

Novel synthesis of thermosensitive porous hydrogels

The simplified method for the synthesis of thermosensitive porous hydrogels by a radical polymerization was presented and their swelling properties were examined experimentally. N,N-Diethylacrylamide (DEAAm) or N-isopropylacrylamide (NIPAm) as primary monomers and N,N′-methylenebisacrylamide (BIS) as a crosslinker were used. They were polymerized in water at various temperatures above the lower critical solution temperature (LCST) of poly-DEAAm (ca. 32°C) or poly-NIPAm (ca. 31°C) by using N,N,N′,N′-,tetramethylethylenediamine (TEMED) and ammonium peroxsodisulfate (APS) as the polymerization accelerator and initiator, respectively. From the observation by a scanning electron microscope, it was found that these gels consisted of aggregated microgel particles, namely, a porous structure. The gels swelled below their LCSTs, and the swelling degree increased with lowering temperature. Furthermore, the gels swelled or shrank very fast in response to the change in temperature, and the shrinking rate was larger than the swelling rate. Such swelling properties and mechanical properties depended on the porous structure of the gels such as the size of the microgels and the pore volume, which largely changed with the synthesis temperature and the component of the primary monomer. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 895–906, 1998     

Temperature‐dependent permeability of polyelectrolyte complex capsule membranes having N‐isopropylacrylamide domains

As a microcapsule with temperature sensitivity, poly(methacrylic acid)–polyethylenimine complex capsules containing N‐isopropylacrylamide units were designed. Two kinds of copolymers of methacrylic acid and N‐isopropylacrylamide were synthesized by free‐radical copolymerization. Partly crosslinked poly(methacrylic acid)–polyethylenimine complex capsules containing the methacrylic acid–N‐isopropylacrylamide copolymers were prepared at 40 or 25°C. The permeation of phenylethylene glycol through the capsule membranes was investigated. Permeability of the capsules prepared at 25°C increased monotonously with increasing temperature from 10 to 50°C. Permeability of the capsules prepared at 40°C also increased with increasing temperature up to 25°C but decreased above 30°C. Also, the degree of swelling of the membranes prepared at 40°C decreased above 30°C. Differential scanning calorimetry measurement showed that N‐isopropylacrylamide units underwent more efficient transition in the capsule membranes prepared at 40°C than in the membranes prepared at 25°C. The capsule membranes prepared at 40°C might have domains in which N‐isopropylacrylamide units are concentrated, whereas these units should distribute uniformly in the capsule membranes made at 25°C. Such a difference in distribution of N‐isopropylacrylamide units might result in the different permeation property of the capsule membranes. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2703–2710, 2000     

Lower critical solution temperature of linear PNIPA obtained from a Yukawa potential of polymer chains

The lower critical solution temperature (LCST) behavior of a linear poly(N‐isopropylacrylamide) (PNIPA) in water is thought to result from the polymer–polymer attractive interaction. This polymer–polymer attraction is modeled by a temperature‐dependent Yukawa attractive potential, with Yukawa parameters determined by fitting the theoretical phase diagram for a pure Yukawa fluid to the experimental lower consolute boundary for a PNIPA–water solution. The predicted coexistence curve for the PNIPA–water mixtures in the temperature‐polymer volume fraction plane is reasonably close to the experimental cloud point data for the PNIPA–water system. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1971–1976, 2000     

固定化酶降解污染水体中有机物及抑制藻类的初步研究

采用海藻酸钙微胶囊包埋固定化酶方法,模拟研究固定化酶降解污染水体中有机物及抑制藻类的效果。考察了固定化纤维素酶和脂肪酶微胶囊的最佳芯壳比及酶浓度的影响,发现酶浓度为1mg/L,芯壳比为1∶3时固定化酶对水中污染物的去除率较高。固定化酶对不同有机物都具有一定的降解作用,但对苯酚等难降解有机物去除率不高,而且对水体中的藻类有抑制作用。模拟天然水体情况下,固定化酶对有机污染物去除效果明显,固定化复合酶去除效果较好且还具有显著的复氧作用。     

Lower critical solution temperatures of thermo‐responsive poly(N‐isopropylacrylamide) copolymers with racemate or single enantiomer groups

BACKGROUND: Thermo‐responsive copolymers with racemate or single enantiomer groups are attracting increasing attention due to their fascinating functional properties and potential applications. However, there is a lack of systematic information about the lower critical solution temperature (LCST) of poly(N‐isopropylacrylamide)‐based thermo‐responsive chiral recognition systems. In this study, a series of thermo‐responsive chiral recognition copolymers, poly[(N‐isopropylacrylamide)‐co‐(N‐(S)‐sec‐butylacrylamide)] (PN‐S‐B) and poly[(N‐isopropylacrylamide)‐co‐(N‐(R,S)‐sec‐butylacrylamide)] (PN‐R,S‐B), with different molar compositions, were prepared. The effects of heating and cooling processes, optical activity and amount of chiral recognition groups in the copolymers on the LCSTs of the prepared copolymers were systematically studied. RESULTS: LCST hysteresis phenomena are found in the phase transition processes of PN‐S‐B and PN‐R,S‐B copolymers in a heating and cooling cycle. The LCSTs of PN‐S‐B and PN‐R,S‐B during the heating process are higher than those during the cooling process. With similar molar ratios of N‐isopropylacrylamide groups in the copolymers, the LCST of the copolymer containing a single enantiomer (PN‐S‐B) is lower than that of the copolymer containing racemate (PN‐R,S‐B) due to the steric structural difference. The LCSTs of PN‐R,S‐B copolymers are in inverse proportion to the molar contents of the hydrophobic R,S‐B moieties in these copolymers. CONCLUSION: The results provide valuable guidance for designing and fabricating thermo‐responsive chiral recognition systems with desired LCSTs. Copyright © 2008 Society of Chemical Industry     

Effect of intermolecular and intramolecular forces on hydrodynamic diameters of poly(N‐isopropylacrylamide) copolymers in aqueous solutions

A novel copolymer, poly(N‐isopropylacrylamide‐co‐hydroxypropyl methacrylate‐co‐3‐trimethoxysilypropyl methacrylate) has been synthesized and the hydrodynamic diameters in various aqueous solutions under different temperatures are determined by dynamic light scattering. The results show that the hydrodynamic diameters of copolymers have no obvious change in each working solution below lower critical solution temperature (LCST); across LCST, the diameters increased suddenly at different initial temperature in various aqueous solutions; above LCST, they decreased slightly as the temperature increased in UHQ water, and increased continuously with increasing temperature or salt concentration in saline solutions, and reduced with the rising of pH value in pH buffer. These are attributed to different intermolecular and intramolecular forces leading to disparity in dimension, conformation, and LCST of copolymers. The hydrogen bonding between water molecules and copolymer chains could maintain size and conformation of copolymer single chain; the hydrogen bonding between amide linkages and hydrophobic interactions between isopropyl groups result in intramolecular collapse and intermolecular aggregation; the electrostatic repulsion weakens aggregation extent of copolymers. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013