Studies on LCST of poly (N-isopropylacrylamide-co-acrylic acid-co-N-diacetone acrylamide)

Linear copolymers from N-isopropylacrylamide （NIPA）, acrylic acid （AA） and diacetone acrylamide （DAA） have been prepared. The effect of composition, ionic strength and pH on their lower critical solution temperature （LCST） has been investigated.

Y-shaped block copolymers of poly(ethylene glycol) and poly(N-isopropylacrylamide) synthesized by ATRP

Novel Y-shaped block copolymers of poly（ethylene glycol） and poly（N-isopropylacrylamide）, PEG-b-（PNIPAM）2, were successfully synthesized through atom transfer radical polymerization （ATRP）. A difunctional macroinitiator was prepared by esterification of 2,2-dichloroacetyl chloride with poly（ethylene glycol） monomethyl ether （PEG）. The copolymers were obtained via the ATRP ofN-isopropylacrylamide （NIPAM） at 30℃ with CuCl/Me6TREN as a catalyst system and DMF/H2O （v/v = 3：1） mixture as solvent. The resulting copolymers were characterized by gel permeation chromatography （GPC） and ^1H NMR. These block copolymers show controllable molecular weights and narrow molecular weight distributions （PDI 〈 1.15）. Their phase transition temperatures and the corresponding enthalpy changes in aqueous solution were measured by differential scanning calorimetry （DSC）. As a result, the phase transition temperature of PEG45-b-（PNIPAM55）2 is higher than that of PNIPAM, however, the corresponding enthalpy change is much lower, indicating the significant influence of the macromolecular composition and architecture on the phase transition.

Reversible Aggregation Kinetics of Poly(N-isopropylacrylamide-co-N-vinylpyrrolidone) in Aqueous Solutions Revealed by Elastic Light Scattering Spectroscopy

Poly（N-isopropylacrylamide-co-N-vinylpyrrolidone） [P（NIPAM-co-NVP）] copolymers with different content of N-vinylpyrrolidone （NVP） were synthesized, and reversible aggregation kinetics of the copolymers in aqueous solutions was investigated with elastic light scattering （ELS） spectra. The results indicated that the apparent activation energy of aggregation process during heating and dissociation process during cooling increased with the NVP content increasing. The phase transition temperature also increased as the content of NVP increased, suggesting that the hydrophilic nature of NVP strongly affected the phase behavior of the copolymer solutions. The higher the content of NVP, the higher the temperature required to break the balance between the hydrophilic and hydrophobie interaction. Besides, during heating and cooling process, the phase transition hysteresis of P（NIPAM-co-NVP） chains decreased when the hydrophilic comonomer increased.

Synthesis and Properties of Poly (N-isopropylacrylamide) and Poly (N-isopropylacrylamide-co-acrylamide) Hydrogels

The thermosensitive poly （ N-isopropylacrylamide ） （PNIPAAm） and poly （N-isopropylacrylamide-co-acrylamide） [ poly （NIPAAm-co-AAm） ] hydrogels with different acrylamide molar percentage are prepared by radiation polymerization using Co^60 γ-ray. Their swelling equilibrium data in the media of deionized water, NaCl aqueous solutions and different pH buffer solutions are determined. It appears that lower critical solution temperature （LCST） of the hydrogels will drop with the increase of ionic strength and increase with the rising of acrylamide content, A semi-empirical formula is set up with the experimental results. Moreover, it also indicates that this copolymer is pH-sensitive, which is similar to the homopolymer of PNIPAAm.

Microwave-assisted Preparation of Temperature Sensitive Poly(N-isopropylacrylamide) Hydrogel with Improved Responsive Properties

Poly（N-isopropylacrylamide）-based hydrogel was prepared under microwave irradiation The hydrogel thus prepared, comparing with that prepared by thermal heating method, exhibits faster swelling and shrinking kinetics. The improved responsive properties are due to the more heterogeneous and porous networks formed under microwave irradiation.

Poly-N-Isopropylacrylamide Hydrogel Based Fluoroimmunoassay of Methyltestosterone

A novel immunoassay method for methyltestosterone (MT) in serum ovas developed.The antigen of MT (Ag(MT))was synthesized by covalently bonding MT to BSA and raising its antibody (Ab(MT)). Ab(MT) was con.jugated to poly-N-isopropylacrylamide (p-NIPAAm) to form Ab(MT) bound thermally reversible hydrogel p-NIPAAm-Ab((MT) A competitive immunoassay method based on the competition of fluorescein isothiocyanate (FITC) labeled MT antigen (FITC-Ag(MT)) and free MT with limited amount of p-NIPAAm-Ab(MT) was established. The separation in the assay process was achieved by precipitation of the immuno-complex above its critical solution temperature. The detection limit for MT is 50ng/ml. The recoveries of MT from human serum are satisfactory.

THERMAL-SENSITIVE BETA-CYCLODEXTRIN-CONTAINING POLY(NISOPROPYLACRYLAMIDE)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.

THE ADSORPTION OF LINEAR POLY(N-ISOPROPYLACRYLAMIDE)CHAINS ON SURFACTANT-FREE POLYSTYRENE NANOPARTICLES

The adsorption of linear poly(N-isopropylacrylamide) (PNIPAM) chains on surfactant-free polystyrene (PS) nanoparticles was used as a model system to study the hydrophobic adsorption of polymer on the surface, because the hydrophobility of PNIPAM can be continuously varied by a small temperature change. The adsorption was investigated by a combination of static and dynamic laser light scattering (LLS) measurements. In static LLS, the absolute excess scattered light intensity led to the amount of PNIPAM adsorbed on the surface. In dynamic LLS, the hydrodynamic thickness of the adsorbed PNIPAM layer was accurately measured. For a given particle concentration, the adsorption increases as the PNIPAM concentration and the incubation temperature increase. The average density of the adsorbed PNIPAM layer is reciprocally proportional to the number of the PNIPAM chains on the surface, revealing a simple scaling of the chain density distribution. The adsorption follows the Langmuir's isotherm. The enthalpy change estimated from the adsorption at 25 degrees C and 30 degrees C is slightly positive, indicating that the adsorption involves the coil-to-globule transition of the chains on the surface.

Poly(N-isopropylacrylamide)-based Vertically Sandwich-typed Hydrogel with Fast Temperature-response Speed and Its Controlled-release Characteristics

A novel poly（N-isopropylacrylamide）-based sandwich-typed hydrogel, which was featured with both ends of linear poly（N-isopropylaerylamide） （PNIPAM） chains being grafted onto cross-linked PNIPAM chains, was successfully prepared in a three-step process by a method of sequential synthesis. The proposed hydrogel displays faster and hydration/dehydration dynamic response to temperature cycling owing to linear PNIPAM chains to form big-pore structure. This work may lead to high attraction for targeting drug delivery systems, polymeric pump, sensors and so on.

Temperature-pH Sensitive IPN Hydrogels Composed of Silk Sericin and Poly(N-isopropylacrylamide)

Interpenetrating polymer network （IPN） composed of silk sericin （SS） and poly（N-isopropylacrylamide） （PNIPAAm） was prepared. The morphology of the IPNs, in which the SS phase was stained with ammonium cuprate, was examined with TEM and a relative homogeneous distribution of the two polymers was exhibited. The swelling behavior of the IPN hydrogels showed both temperature and pH dependences.

Thermo-Responsive Electrospun Nanofibers from Poly( N-isopropylacrylamide )/Polyvinyl Pyrrolidone Blends

A novel nanofiber composite poly(N-isopropylacrylamide)(PNIPAAm)/polyvinyl pyrrolidone(PVP)was successfully prepared by electrospinning.Analogous medicated fibers loaded with ketoprofen(KET)as a model drug were prepared.X-ray diffraction(XRD)demonstrated that the drug was presented in the fibers with an amorphous form.Both scanning and transmission electron microscopy showed that the fibers had an even diameter and smooth surface,and no phase separation was observed.The KET loaded nanofibers did not affect the morphology of the fibers,and no drug aggregation was separated from the polymer fibers.Water contact angle measurements proved that the PNIPAAm/PVP fibers switched from hydrophilic to hydrophobic when the temperature increased the lower critical solution temperature of 32℃.In vitro drug release studies were also undertaken and the result indicated that the PNIPAAm/PVP blend nanofiber presented the properties of the two polymers,having temperature-sensitive systems with sustained release properties.In addition,MTT assay demonstrated that the nanofiber film was non-toxic and suitable for cell growth.Thus,the nanofiber can be used as thermoresponsive carriers for sustained release of poor water soluble drugs.

Preparation and chromatographic evaluation of thermoresponsive N-isopropylacrylamide copolymers stationary phases containing amino groups

Two cationic thermoresponsive stationary phases were designed and prepared containing poly [ N-isopropylacrylamide-co-（ 2-dimethylamino ） ethylmethacrylate ] and poly [ N-isopropylacryl- amide-co-（2-diethylamino） ethylmethacrylate] via a simple method, the direct copolymerization of monomers with double bonds on silica surfaces. The two copolymers were synthesized by radical polymerization and then characterized using Fourier transform infrared and gel permeation chroma- tography. The thermoresponsive property and amounts of copolymers grafted on silica were deter- mined through transmittance measurements and thermogravimetric analysis, respectively. The copol- ymers grafted silica particles were then applied as high-performance liquid phase （HPLC） stationary phases for chromatographic separation. Chromatographic properties of mobile phases at different pH values were evaluated by changing temperatures and using benzene and hydrocortisone as the test an- alytes. Retention time of the analytes was prolonged with increasing temperature on both thermore- sponsive columns due to enhanced hydrophobic interaction between analytes and stationary phases. The resolution increased with increasing pH of mobile phase. The optimal separation was obtained at phosphate buffer solution （ 10 raM, pH 8. 0） and at 50 ℃. The pH of mobile phase had a crucial effect on separation efficiency. The results illustrated that poly（ N-isopropylacrylamide-co-（2-diethyl- amino） ethylmethacrylate ] copolymer modified silica was more advantageous for the temperature-re- sponsive chromatographic separation because its lower critical solution temperature was relatively lower compared to the poly [ N-isopropylacrylamide-co-（2-dimethylamino） ethylmethacrylate ] sta- tionary phase.

Laterally Sandwich-typed Hydrogel Columns with Liner Poly(N-isopropylacrylamide) Layer:Preparation, Swelling/deswelling Kinetics and Drug Delivery Characteristics

A novel thermo-responsive hydrogel column, featured with both ends of linear poly（N- isopropylacrylarnide） （PNIPAM） chains being grafted onto cross-linked PNIPAM chains, was reported. The laterally sandwich-typed hydrogel columns were fabricated by radical polymerization in a three-step process using a method of ice-melting synthesis. The initiating path, morphology and thermoresponsive characteristics of the prepared hydrogel columns were experimentally studied. The results show that the hydrogel column obtained by the initiator inside part has more quick swelling and deswelling rates responsing to temperature cycling than other hydrogels owing to linear PNIPAM chains to form supermacroporous structure. The proposed hydrogel structure provide a new mode of the phase transition behavior for thermo-sensitive ＂smart＂ or ＂intelligent＂ monodisperse micro-actuators, which is highly attractive for targeting drug delivery systems, chemical separations, and sensors and so on.

N⁃苯基马来酰亚胺共聚物的合成及对PVC树脂耐热改性效果研究

通过种子乳液聚合结合半连续加料方式,成功聚合出分子结构一致且与聚氯乙烯(PVC)树脂具有良好相容性的聚(N‐苯基马来酰亚胺‐苯乙烯‐丙烯腈)(PNSA)共聚物胶乳,将其与PVC树脂直接复合制备PNSA/PVC复合材料,并对PNAS耐热改性的效果进行评价。结果表明,PNSA纳米胶乳颗粒粒径在155.3~251.5 nm之间,粒径分布均一;PNSA共聚物分子组成呈无规结构,分子结构一致,差示扫描量热曲线呈现单一的玻璃化转变温度(T_(g)),且与PVC树脂具有极佳的相容性;PNSA含量由0升高至50%(质量比,下同)时,复合材料的T_(g)由84.8℃提高到107.2℃,提高了22.4℃,维卡软化温度由71.2℃提高到91.9℃,提高了20.7℃;除耐热性改善以外,复合材料的力学性能也有一定程度的提高,本文的研究有利于PVC应用领域的进一步拓展。

偶氮苯基小分子光控聚N-异丙基丙烯酰胺在离子液体中的自组装

偶氮苯基材料因其具有可逆的光致顺反异构特性,可调控聚合物的自组装行为而受到广泛关注。采用不同结构且广泛商业化的偶氮苯基小分子(偶氮苯(AZO)、对羟基偶氮苯(AZO-OH)、对氨基偶氮苯(AZO-NH2)、二甲基黄[AZO-N(CH_(3))_(2)])作为光分子开关,控制聚N-异丙基丙烯酰胺(PNIPAm)在1-乙基-3-甲基咪唑双(三氟甲基磺酰基)亚胺([C2mim][NTf_(2)])离子液体中的自组装行为,探讨不同偶氮苯基末端基元对于PNIPAm自组装相行为的影响。结果表明,偶氮苯基小分子均能有效调控PNIPAm在[C2mim][NTf_(2)]离子液体中的相变响应行为,但不同的末端基元对于PNIPAm的相变温度及相变区间影响甚微。结合原位变温红外谱图分析可知,紫外光照强化了PNIPAm与离子液体之间的相互作用,从而抑制了PNIPAm侧链间的相互聚集,这将促进紫外光照条件下“溶剂化”效应的发生,可获得更低的相变温度。

PNIPAm@CMCS生物基水凝胶吸附染料研究

针对目前皮革废水处理剂难回收问题,以羧甲基壳聚糖(CMCS)和聚N-异丙基丙烯酰胺(PNIPAm)为原料,合成一种兼具优异吸附性和可重复利用且易回收的生物基水凝胶(PNIPAm@CMCS),并对该水凝胶的抗疲、亲水、溶胀、吸附及抗菌等性能进行了研究。结果表明,所制备的生物基水凝胶具有出色的抗疲性(耐循环压缩15次)、溶胀率(2034%)、吸附性(伊红Y=587 mg/g,罗丹明=444 mg/g,甲基橙=621 mg/g)和抗菌性能(抗菌率=100%)。该生物基水凝胶作为一类高效、环保的染料废水处理剂,展现了广阔的应用前景,有望为制革工业处理含染料污水提供新的思路。

智能窗口用热响应聚(N-异丙基丙烯酰胺)水凝胶的研究进展

本文综述了智能窗口用热响应聚(N-异丙基丙烯酰胺)水凝胶的热响应机理,介绍了该水凝胶材料的制备方法及相关的性能,阐述了影响PTC效应的主要因素及提高其稳定性的方法,展望了智能窗口用热响应聚(N-异丙基丙烯酰胺)水凝胶未来的研究方向和发展前景。

基于n型柔性半导体的有机晶体管及其电子-离子双响应特性

为了研究n型有机混合离子电子导体电子-离子双响应特性及分子量对载流子迁移率的影响,采用具有平面刚性的梯形分子链结构的高分子量聚苯并二咪唑苯并菲绕啉二酮制备高性能有机电化学晶体管,并对晶体管紫外可见吸收光谱和晶体管器件电气性能进行表征。结果表明,利用高分子量聚苯并二咪唑苯并菲绕啉二酮制备的n型有机电化学晶体管表现出极高的响应速度(0.034 s)、高载流子迁移率(4.72×10^(-3) cm^(2)/(V·s)),以及在水系电解液中优异的稳定性(稳定运行超过120次脉冲循环)。

聚N-异丙基丙烯酰胺/聚丙烯酸水凝胶的制备及性能研究

当外界环境发生变化时,环境敏感型水凝胶的物理性质或化学性质会随之发生改变,大部分水凝胶对环境的响应比较单一。以丙烯酸(AA)和N-异丙基丙烯酰胺(NIPAm)为原料制备的聚N-异丙基丙烯酰胺/聚丙烯酸水凝胶既可以对温度变化也可以对pH值变化做出响应。实验采用一锅法制备了聚N-异丙基丙烯酰胺/聚丙烯酸水凝胶,通过调节丙烯酸的中和度、丙烯酸(AA)和N-异丙基丙烯酰胺(NIPAm)两种单体的配比、交联剂N,N′-亚甲基双丙烯酰(BIS)和引发剂过硫酸钾(KPS)的用量,研究其对水凝胶的吸水性能、拉伸性能的影响,并考察了所制备的聚N-异丙基丙烯酰胺/聚丙烯酸水凝胶对温度及pH响应性能。实验结果表明:当丙烯酸的中和度为125%、n(NIPAm)∶n(AA)=0.3∶1、BIS的质量分数为0.5%、KPS的质量分数为1%时,制备的水凝胶溶胀率最大且有一定的弹性,室温下吸水率达179.73 g/g。该水凝胶在酸性缓冲溶液(pH值=3)中收缩,当缓冲溶液的pH值大于3,水凝胶发生溶胀,具有灵敏可逆的pH响应性能,同时该水凝胶兼具热缩温敏性能。

含PNIPAM嵌段有机纳米管的合成及其对MB与ARS的吸附与释放性能探究

为了高效吸附染料废水中的染料分子,制备了一种具有温度可控性的新型吸附材料。首先,采用可控自由基聚合和开环聚合将聚N-异丙基丙烯酰胺(PNIPAM)引入多孔有机纳米管中,制备了具有核壳结构的多组分聚合物分子刷;其次,利用分子刷嵌段聚合物的傅克烷基化超交联过程生成了具有微孔、中孔和大孔结构的PNIPAM修饰的多级孔有机纳米管网络(MONNs)聚合物;最后,探究了MONNs对染料分子亚甲基蓝(MB)、茜素红S(ARS)的吸附与释放性能。结果表明,该方法制备的MONNs材料对染料分子具有良好的吸附效果。