聚N,N-二乙基丙烯酰胺溶液粘度的温度依赖性

通过自由基聚合,合成了线型聚N,N-二乙基丙烯酰胺（PDEA）,用乌氏粘度计测定并考察了该聚合物在四氢呋喃（THF）、H2O以及THF-H2O混合溶剂中粘度的温度依赖性.实验结果表明,PDEA 在上述三种溶剂中粘度的温度依赖性不同，PDEA-THF体系的相对粘度随温度升高而增大；PDEA-H2O体系以及PDEA-THF-H2O体系的相对粘度随温度升高而减小,且THF体积分数φTHF < 0.7时具有透明-白浊转变现象；对PDEA-THF-H2O体系,φTHF增加,透明-白浊转变温度升高,而当φTHF=0.7时,则观察不到透明-白浊转变现象.     

腐植酸钠/聚N-异丙基丙烯酰胺/粘土杂化水凝胶的合成及脱色性能

以N-异丙基丙烯酰胺单体、粘土和腐植酸钠为原料合成了温敏腐植酸钠/聚N-异丙基丙烯酰胺/粘土（SH/PNIPA/clay）系列水凝胶。用红外光谱分析仪对其内部相互作用进行了研究,并用紫外可见分光光度计对水凝胶吸附-解吸亚甲基蓝的性能进行了测试。实验结果表明凝胶中SH与PNIPA形成了氢键;凝胶对亚甲基蓝（MB）的吸附和解吸能力受腐植酸钠的含量、粘土含量、亚甲基蓝的起始浓度和温度的影响。２％粘土含量和低温条件有利于凝胶吸附和解吸。     

聚N,N-二乙基丙烯酰胺低聚物水溶液的分子动力学研究

对50个单元构成的聚N,N-二乙基丙烯酰胺(PDEA)低聚物的水溶液体系进行了分子动力学的研究,分别模拟了300 K时的伸展链、310 K时的伸展链以及紧缩链与水构成的体系,对溶液中PDEA周围溶剂水分子的分布情况以及水分子形成氢键的情况进行了统计,结果表明在PDEA周围的水产生了比本体水更有序的结构,形成了更多的氢键,这种有序结构维持到第二水合层甚至更远.发生相分离后,PDEA与水分子形成的氢键大部分未被破坏,水合层中每个水分子形成的氢键数也没有明显变化,但水合层(形成有序结构的水分子)内水分子数目的减少使得总的氢键数目减少,从而造成体系能量增加及熵增加.同时还研究了聚合物及水分子的自扩散系数,表明PDEA影响周围水分子结构的同时,对水的动力学性质也产生了很大影响.     

多孔聚N-异丙基丙烯酰胺水凝胶的制备与缓释性能

以N-异丙基丙烯酰胺(NIPA)、N,N-亚甲基双丙烯酰胺(MBA)和聚乙二醇(PEG)为原料,以60Co-γ射线为放射源制备了快速响应聚N-异丙基丙烯酰胺(PNIPA)多孔水凝胶。用红外光谱分析了水凝胶的结构,并测定了水凝胶的溶胀动力学、退溶胀动力学和平衡溶胀率。结果表明,PEG分子仅在聚合交联过程中充当成孔剂,不参与反应,反应后可被除去;水凝胶具有明显的温度敏感性,成孔剂的添加提高了水凝胶的溶胀性能和LCST。选用阿司匹林为模型药物,对水凝胶的药物缓释性能进行了初步研究。     

聚N-异丙基丙烯酰胺/纳米SiO2复合水凝胶的合成及溶胀性能

通过纳米SiO2的表面功能化,在其表面引入乙烯基功能基团,在H2O／THF的混合溶剂中,超声分散后,交联剂N,N′-亚甲基双丙烯酰胺存在时,于25℃下使其与N-异丙基丙烯酰胺共聚,制得聚N-异丙基丙烯酰胺,纳米SiO2复合水凝胶,并用FT-IR和SEM对产物进行了表征,研究了凝胶的溶胀动力学,消溶胀动力学和温度敏感性,实验结果表明,纳米SiO2的引入,改善了聚N-异丙基丙烯酰胺水凝胶在低温时的溶胀性能和在高温时对水的释放性能,并讨论了引起这些性能改变的原因。     

PDEA和P(DEA-co-NHMAA)稀水溶液相分离行为研究

运用紫外-可见分光光度法分别考察了聚N,N-二乙基丙烯酰胺(PDEA)和N-羟甲基丙烯酰胺(NHMAA)与DEA的共聚物P(DEA-co-NHMAA)稀水溶液相分离行为. 结果发现，当P(DEA-co-NHMAA)中NHMAA的质量分数小于5.25%时, 随着NHMAA含量的增加， 其最低临界溶解温度(TLCS)下降；当NHMAA的含量大于5.25%时，随着NHMAA含量的增加，其TLCS上升；与PDEA相比P(DEA-co-NHMAA)相分离行为的浓度依赖性减弱；PDEA和P(DEA-co-NHMAA)从无规线团(coil)到蜷曲球(globular)的突然转变与从globular到coil的逐渐转变机理不同. 据此提出了P(DEA-co-NHMAA)在稀水溶液中相变的分子机理.     

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。     

具有智能荧光特性的含二甲氨基查尔酮端基的PNIPAM研究

以偶氮二异丁腈为引发剂,含二甲氨基查尔酮基团的三硫代碳酸酯为链转移剂,在四氢呋喃溶剂中将N-异丙基丙烯酰胺(NIPAM)通过可逆加成断裂链转移(RAFT)自由基聚合制备了具有智能荧光特性的含二甲氨基查尔酮端基的聚N-异丙基丙烯酰胺(PNIPAM-DMAC),并通过红外光谱、核磁共振氢谱和紫外-可见光谱对其结构进行表征.研究了PNIPAM-DMAC聚合物的温敏性以及溶剂极性、温度、分子识别三重敏感的荧光特性.结果表明,PNIPAM-DMAC聚合物的低临界溶解温度(LCST)比聚N-异丙基丙烯酰胺(PNIPAM)聚合物低,且随着PNIPAM-DMAC聚合物分子量的降低、聚合物水溶液浓度的减小和α-环糊精(α-CD)的加入,其LCST温度均升高.随着溶剂极性的增加,PNIPAM-DMAC聚合物的荧光峰值波长基本上随着溶剂极性的增大而红移,荧光强度出现极小值和极大值,在甲醇和水中几乎无荧光,具有溶剂极性敏感的荧光特性;随着温度升高,PNIPAM-DMAC聚合物水溶液荧光强度显著增强,同时伴随荧光发射光谱的蓝移现象,且荧光随温度交替改变而呈现出可逆变化,具有可逆的温度“开/关”特性;α-CD的添加使得PNIPAM-DMAC聚合物水溶液的荧光强度增强,荧光峰值波长轻微蓝移,具有分子识别敏感的荧光特性.     

聚丙烯酸-b-聚(N-异丙基丙烯酰胺)嵌段共聚物的合成及其温度和pH值敏感性自组装研究

通过原子转移自由基聚合方法, 在丁酮/异丙醇混合溶剂中合成了分子量可控和分布较窄的聚丙烯酸叔丁酯-b-聚N-异丙基丙烯酰胺(PtBA-b-PNIPAM)嵌段共聚物, 用GPC和 1 H NMR对其结构进行了表征. PtBA-b-PNIPAM在甲苯中水解得到聚丙烯酸-b-聚N-异丙基丙烯酰胺(PAA-b-PNIPAM). 用动态光散射技术对PAA-b-PNIPAM在水溶液中的自组装行为随pH值和温度变化的响应进行了初步研究.     

有无N-异丙基丙烯酰胺制备纳米微胶囊机理的比较

通过研究交联剂对颗粒形态的影响, 提出小分子烃的逃逸是导致生成大量小尺寸实心粒子的主要原因, 而交联剂的加入在一定程度上能抑制小分子烃的逃逸. 将N-异丙基丙烯酰胺单体引入小分子烃为模板的细乳液聚合法制备的纳米微胶囊体系中, 水相引发形成的聚N-异丙基丙烯酰胺(PNIPA)齐聚物自由基在聚合温度下(大于最低临界溶液温度)析出并被细乳液液滴吸附, 在热力学推动力和静电斥力的共同作用下, PNIPA齐聚物倾向于分布在液滴和水的界面上, 使液滴界面成为主要的聚合场所, 单体从液滴内部向界面扩散补充消耗的单体, 生成的聚合物在液滴界面上析出, 包覆小分子烃液滴, 最终得到纳米微胶囊.     

FTIR study on molecular structure of poly(N-isopropylacrylamide) in mixed solvent of methanol and water

The intrachain and interchain hydrogen bonding of poly(N-isopropylacrylamide) (PNIPA) and intermolecular hydrogen bonding between PNIPA chains and the solvent molecules in the mixed solvent of methanol and water have been quantitatively investigated by using Fourier transform infrared (FTIR) spectroscopy at 25 °C. In this spectroscopic system with curve fitting program, we found that in the C-H stretching region, both the N-isopropyl group and the backbone underwent conformational change upon the solvent composition. An analysis of the amide I band suggested that the amide groups of PNIPA were mainly involved in intermolecular hydrogen bonding with water molecules, and the polymer chains were flexible and disordered in the mixed solvent when the methanol volume fraction (χ_v) was lower than 15%. While χ_v was in the range of 15-65%, about 30% of these intermolecular hydrogen bonding between the polymer and water were replaced by intrachain and interchain hydrogen bonding, consequently, PNIPA shrinked as aggregates. If χ_v was above 65%, the interchain hydrogen bonding became predominant due to the solubility characteristics of amphiphilic methanol, and the PNIPA system was homogeneous solution again. We believe that the reentrant transition is related to the weaker interaction between PNIPA molecules and methanol-water complexes, (H₂O)_m(CH₃OH)_n (m/n = 5/1, 5/2, 5/3, 5/4, 5/5) as compared to that between PNIPA and free water or free methanol.     

Small-angle neutron scattering study on microstructure of poly(N-isopropylacrylamide)-block-poly(ethylene glycol) in water

By employing small-angle neutron scattering (SANS), we investigated the microstructures of, poly(N-isopropylacrylamide) (PNIPA)-block-poly(ethylene glycol) (PEG) (NE) in deuterated water D₂O, as related to macroscopic behaviors of fluidity, turbidity and synerisis. SANS revealed following results: (i) microphase separation occurs at around above 17 °C in a temperature range of transparent sol below 30 °C. In the microdomain appeared in the transparent sol state, both block chains of PNIPA and PEG are swollen by water; (ii) for the NE solution of polymer concentration W_p > 3.5% (w/v), corresponding to opaque gel above 30 °C, a percolated structure, i.e., network-like domain is formed by NE as a result of macrophase separation due to dehydration of the PNIPA chains. As the temperature increases toward 40 °C, the network domain is squeezed along a direction parallel to the NE interface, which leads to increase of the interfacial thickness given by swollen PEG chains and to the macroscopic synerisis behavior.     

Synthesis and characterization of Poly(N-isopropylacrylamide)/Poly(acrylic acid) semi-IPN nanocomposite microgels

A novel pH- and temperature-sensitive nanocomposite microgel based on linear Poly(acrylic acid) (PAAc) and Poly(N-isopropylacrylamide) (PNIPA) crosslinked by inorganic clay was synthesized by a two-step method. First, PNIPA microgel was prepared via surfactant-free emulsion polymerization by using inorganic clay as a crosslinker, and then AAc monomer was polymerized within the PNIPA microgel. The structure and morphology of the microgel were confirmed by FTIR, WXRD and TEM. The results indicated that the exfoliated clay platelets were dispersed homogeneously in the PNIPA microgels and acted as a multifunctional crosslinker, while the linear PAAc polymer chains incorporated in the PNIPA microgel network to form a semi-interpenetrating polymer network (semi-IPN) structure. The hydrodynamic diameters of the semi-IPN microgels ranged from 360 to 400 nm, which was much smaller than that of the conventional microgel prepared by using N,N′-methylenebis(acrylamide) (MBA) as a chemical crosslinker, the later was about 740 nm. The semi-IPN microgels exhibited good pH- and temperature-sensitivity, which could respond independently to both pH and temperature changes.     

Reentrant behavior of poly(N-isopropylacrylamide) brushes in water-methanol mixtures investigated with a quartz crystal microbalance

The solvent composition induced reentrant behavior of poly(N-isopropylacrylamide) (PNIPAM) chains grafted on a SiO2 surface in water-methanol mixtures was investigated using a quartz crystal microbalance with dissipation monitoring (QCM-D) at 20 degrees C. The frequency and energy dissipation responses showed that the grafted PNIPAM chains sharply collapse when the methanol content (x(m)) reaches approximately 17 mol %. In the range 17-50 mol %, the grafted chains remain in a collapsed state. Further increase of the methanol content leads to an abrupt reswelling of the collapsed chains at x(m) > approximately 50 mol %. The sharp reentrant swelling-to-collapse-to-swelling transition was attributed to the water-methanol complexation instead of the preferential adsorption effect. Our results also suggest that the water-methanol complexation is not induced by hydrophobic interaction but by hydrogen bonding.     

聚丙烯酰胺-聚乙二醇-水体系相图及丙烯酰胺单体在两相中的分配

聚丙烯酰胺(PAAm)和聚乙二醇(PEG)两种水溶液混合时能形成双水相体系,其中上层为PEG富集相,下层为PAAm和PEG的混合相.用凝胶渗透色谱(GPC)法和浊度滴定法研究了PAAm-PEG-H₂O双水相体系的相图,结果表明,随着PEG分子量的升高,体系的分相浓度下降.在PAAm-PEG20000-H₂O体系中,随着体系温度升高,分相浓度先下降后升高,55℃时分相浓度最低.丙烯酰胺(AAm)单体能在两相中发生相分配,分配系数随着PAAm浓度和平衡温度的增加而增大,随着PEG浓度的增加而下降.     

Poly[2-(N,N-Dimethylamino) Ethyl Methacrylate] /Poly(Styrene-Co-Methacrylic Acid) Interpolymer Complexes

Summary: Poly[2-(N,N-dimethylamino)ethyl methacrylate] (PDMAEMA), copolymers of different compositions of styrene with 2-(N,N-dimethylamino)ethyl methacrylate (SDMAEMA) or methacrylic acid (SMA) were synthesized by free radical polymerization and characterized by several techniques. Different ternary mixtures containing proton-acceptors PDMAEMA or SDMAEMA, proton-donor copolymers SMA and a solvent (butan-2-one or THF) were prepared. The present study, that investigated several factors that affected the phase behaviors of the ternary mixtures above, confirmed that, indeed depending on the nature of solvent, densities of interacting species, amounts of efficient specific interactions that occurred between the two copolymers, interpolymer complexes of different structures were elaborated. The complexation phenomena, observed with these different systems were analyzed in solution by viscometry that confirmed these effects in monitoring the formation of interpolymer complexes. The specific interactions that occurred between pairs of polymers of each system above were qualitatively evidenced by FTIR spectroscopy from the appearance of new bands or their new redistribution. The glass transition temperature Tg of the obtained complexes of different structures determined by DSC varied differently with the weight fraction of one of the copolymers. These various Tg-compositions were analyzed using the Kwei and Brostow et al. approach recently developed. Thermal analysis of some of the elaborated complexes, examined by thermogravimetry, confirmed their improved thermal stability.     

Photo-grafting Poly(acrylic acid) onto Poly(lactic acid) Chains in Solution

Poly(lactic acid)(PLA)is one of the most important bio-plastics,and chemical modification of the already-polymerized poly(lactic acid)chains may enable optimization of its material properties and expand its application areas.In this study,we demonstrated that poly(lactic acid)can be readily dissolved in acrylic acid at room temperature,and acrylic acid can be graft-polymerized onto poly(lactic acid)chains in solution with the help of photoinitiator benzophenone under 254 nm ultraviolet(UV)irradiation.Similar photo-grafting polymerization of acrylic acid(PAA)has only been studied before in the surface modification of polymer films.The graft ratio could be controlled by various reaction parameters,including irradiation time,benzophenone content,and monomer/polymer ratios.This photo-grafting reaction resulted in high graft ratio(graft ratio PAA/PLA up to 180%)without formation of homopolymers of acrylic acid.When the PAA/PLA graft ratio was higher than 100%,the resulting PLA-g-PAA polymer was found dispersible in water.The pros and cons of the photo-grafting reaction were also discussed.