交联大分子的合成与表征

设计了含有分子内反应和分子间反应的聚合体系，这是一对竞争反应，竞争的结果可达到一定的平衡，使无法控制的凝胶化过程得以控制，从而合成了具有交联结构的大分子。通过分子尺寸的测定还发现了交联大分子在溶液中的特殊行为，这种特殊行为恰好验证了所合成的大分子具有交联结构。     

可溶性交联大分子的合成及稀溶液行为

在浓溶液中合成了可溶性交联大分子（ICM）,研究了不同交联度,不同浓度下聚氨酯交联大分子,系列样品在溶液中的行为。发现这样的大分子在溶液中通过分子之间的物理作用易于相互粘接形成分子簇,且这种分子间作用的大小及其分布对交联度有很大的依赖。交联度不同的大分子,溶液行为有很大的差别。透射电镜显示交联大分子有着千差万别的特殊形状,这些形状还显示了交联大分子可能存在一个特殊的成长过程。     

可控交联聚合的设计

用分子链上含有50~200个羟基的聚乙烯醇缩丁醛(PVB)与4,4′-二苯甲烷二异氰酸酯(M D I)组成了一个交联聚合体系。反应初期首先形成分子链上含有-NCO和-OH基团的预聚物分子。预聚物分子在溶液中呈无规线团形态,并存在线团内和线团间反应,由于这是一对竞争反应,所以使交联过程得以控制。PVB分子的官能度与M D I用量可以改变分子内和分子间反应的数量,这正是控制交联过程及设计具有有限分子量的可溶性交联大分子所需要的。     

聚氯乙烯与丁腈橡胶交联反应的分子模拟

用分子模拟方法对聚氯乙烯(PVC)与丁腈橡胶(NBR)化学交联机理及交联反应位置进行了研究,通过DMol 3计算反应的自由能、活化能和反应热,进而研究他们对交联反应行为的影响。模拟结果显示:在453K时,过氧化二异丙苯(DCP)能够引发NBR发生夺取α-亚甲基活泼氢的反应和双键的加成反应,产生NBR大分子自由基,进而引发NBR的自交联反应,加成反应的速率要快于夺取α-亚甲基活泼氢的反应速率;DCP能够引发PVC发生脱氢反应,形成PVC大分子自由基进而引发PVC的交联,但不能引发PVC发生脱氯的反应;PVC与NBR能够发生共交联反应;NBR的自交联反应最快,PVC与NBR的共交联反应次之,PVC的自交联反应最慢。     

基于环糊精包合的超分子水凝胶骨修复材料

分别合成聚β-环糊精作为主体分子及侧链含有金刚烷胺和阿仑膦酸的聚合物作为客体分子,对其化学结构与相对分子质量进行了核磁共振氢谱表征。通过环糊精和金刚烷胺的主客体的分子相互作用得到一种物理交联的超分子水凝胶。通过对聚β-环糊精溶液粒径大小的表征,发现其粒径均匀,平均粒径大小为8.773 nm。倒立法研究发现,主客体分子比例为8∶1时形成的凝胶粘附性能最强。通过流变测试,验证了水凝胶的凝胶化过程。该体系中的阿仑膦酸基团能为水凝胶和骨创伤界面提供强的粘合作用,因而本体系可用于制备可注射水凝胶应用于骨修复领域。     

双交联聚乙烯醇/海藻酸钠水凝胶的制备与表征

以聚乙烯醇(PVA)与海藻酸钠(SA)为原料,利用CaCl_2/硼酸溶液进行化学交联,再通过循环冷冻解冻物理交联,制备出PVA/SA水凝胶。分析讨论了水凝胶的交联机理、结构、力学性能、含水率、孔隙率及细胞相容性。红外光谱分析表明,经CaCl_2/硼酸溶液交联后,Ca~(2+)与SA中的-COO~-形成络合,硼酸溶液中B(OH)_4~-与PVA交联形成交联结构,循环冷冻解冻促使了复合水凝胶中分子间和分子内氢键的形成。扫描电镜测试表明,PVA/SA水凝胶内部具有丰富的多孔结构,孔径约5～30μm。水凝胶的性能可通过交联剂浓度等进行调控,其中m(PVA)/m(SA)为8∶2,交联剂质量分数为5%时,水凝胶压缩模量和压缩强度分别达到(121.84±3.03) kPa和(636.18±68.71) kPa;含水率和孔隙率分别为83.73%和79.98%。细胞培养结果表明,双交联PVA/SA水凝胶细胞相容性良好。     

聚N—羟甲基丙烯酰胺—间苯二酚气凝胶合成与表征

报导了一种新型气凝胶的准备方法。Ｎ－羟甲基丙烯酰胺和间苯二酚混合溶液采用辐射引发聚合，经加热交联、熔剂交换和超监界干燥，形成有机气凝胶。ＮＭＲ、ＩＲ和Ｒａｍａｎ光谱证实交联是通过酚醛缩合方式进行的，经透射电镜与ＢＥＴ比表面积测定表明，此有机气凝胶具有一般气凝胶的微观结构。     

基于溶剂置换的壳聚糖水凝胶的构建及力学性能研究

采用碱液置换丙二醇的方法制备物理交联壳聚糖水凝胶,研究了碱液浓度及三聚磷酸钠（TPP）离子交联预处理对凝胶结构和力学性能的影响。SEM观察结果表明水凝胶微观结构为富有纳米纤维的三维网络结构,且离子交联预处理在一定程度上会影响水凝胶内部结构的形成。无侧限压缩测试和动态力学分析（DMA）结果显示,未经离子交联的水凝胶在NaOH溶液浓度≤4mol/L时,力学性能随碱溶液浓度增大而增加,在NaOH溶液浓度为4mol/L时获得最优的力学性能;TPP交联后再经NaOH溶液处理的水凝胶其力学性能有所下降,当NaOH溶液浓度为2mol/L时可获得最优的力学性能。采用的2种物理交联方式在水凝胶形成过程中具有竞争关系。     

pH响应微凝胶的表面功能化及巯基-迈克尔加成交联研究

静电引力法表面修饰pH-响应微凝胶聚(甲基丙烯酸甲酯/甲基丙烯酸)[P(MMA/MAA)],在pH诱导下发生微凝胶的颗粒溶胀和化学耦合作用,形成二次交联微凝胶基水凝胶。分别以丙烯酰氧乙基三甲基氯化铵(DAC)和β-巯基乙胺盐酸盐为功能性修饰剂对P(MMA/MAA)进行表面修饰,获得DAC-P(MMA/MAA)和表面巯基化修饰的微凝胶[HS-P(MMA/MAA)]两种不同的微凝胶。弱碱性条件下(pH≈8),功能化修饰的微凝胶之间发生巯基-迈克尔加成的偶联反应,形成二次交联的微凝胶基水凝胶。流变学研究表明,二次交联微凝胶的水凝胶储能模量与同条件下未经修饰的微凝胶形成的物理凝胶相比升高了4倍多。     

手性超分子凝胶材料的研究进展

超分子凝胶作为一类新型的智能自组装软材料,从分子水平到微纳米水平的组装过程中,手性发挥了重要的作用.一般情况下,手性信号都是直接从分子转换到纳米纤维中,但也有一些有趣的现象,即混合两种对映体可以调控得到不同手性形态的纤维结构,甚至一些本身不具备手性的构筑块同样可以通过外界诱导得到具有手性结构的组装体.对纤维手性自组装机理的研究不仅揭示了分子手性到纤维微纳米手性转换这一重要过程,而且对新型的手性材料和微纳米器件的开发也有启发作用.有关微纳米水平的手性材料在手性识别、不对称催化、生物大分子结晶和无机材料的手性模板剂、生物医用等领域的应用研究也逐渐得到重视.主要综述了近二十年来有关手性超分子凝胶的研究,主要从凝胶因子的手性自组装、手性在分子水平和微纳米水平上的形貌调控和表征方法、超分子凝胶的手性应用几个方面进行概述,并对手性超分子凝胶的应用和研究前景进行了展望.     

羧甲基纤维素系列高分子表面活性剂在溶液中分子形态的研究

通过激光光散射和粘度法研究了羧甲基纤维素（ＣＭＣ）与烷基醇聚氧乙烯醚丙烯酸酯（ＡＲ１２ＥＯｎ）的超声共聚物在溶液中的分子形态。结果表明，随活性大单体支链增长，共聚物分子尺寸增大；水溶液中的胶束粒子随共聚物的疏水性增强而增大，ＣＭＣ－ＡＲ１２ＥＯ３体系胶束聚集数最大；共聚物分子与胶束均呈棒状结构。共聚物水溶液的粘度主要取决于分子量和胶束缔合数，盐水溶液中的粘度异常行为与共聚物中引入的大单体活性及形成的胶束结构有关。     

THE USE OF SIMULATED FRACTALS IN THE ANALYSIS OF AGGREGATES

A procedure is described for the simulation of clusters and aggregates which are constrained to have a definite fractal dimension. The fractal (Hausdorff-Besicovitch) dimension of the simulated clusters was determined for two dimensional projections of clusters using methods based on the radius of gyration and ¹Voss. The two approaches are compared and used to develop a correlation between the fractal dimension of the cluster and its two dimensional projection.     

Poly (N-isopropylacrylamide) microgels for organic dye removal from water

The ability of poly (N-isopropylacrylamide) (pNIPAm), and pNIPAm-co-acrylic acid (pNIPAm-co-AAc) microgels to remove an organic azo dye molecule, 4-(2-Hydroxy-1-naphthylazo) benzenesulfonic acid sodium salt (Orange II) from aqueous solutions at both room and elevated temperature was assessed. At room temperature, we found that the amount of Orange II removed from water (removal efficiency) increased with increasing AAc and microgel concentration. The removal of Orange II from water was also fit by a Langmuir sorption isotherm model. Furthermore, we found the extent of Orange II removal depended on solution temperature; more Orange II was removed from water at elevated temperature and as the microgels were held at that temperature for longer durations of time. Additionally, by increasing the cycles between high and ambient temperature, the removal of Orange II was enhanced, although this was only true for two temperature cycles. We hypothesize that this is a result of the thermoresponsive nature of pNIPAm-based microgels which deswell at elevated temperature expelling their solvating water and when the microgels are cooled back down they reswell with the Orange II containing water. We also hypothesize that the microgels become saturated after the second heating cycle and so the efficiency of removal did not increase further. Finally, we assessed the ability of the microgels to retain the Orange II after it is removed from the aqueous solution. We determined that the microgels "leak" 25.6% of the Orange II that was originally removed from the water.     

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.     

Hot Brownian Motion of Thermoresponsive Microgels in Optical Tweezers Shows Discontinuous Volume Phase Transition and Bistability

Microgels are soft microparticles that often exhibit thermoresponsiveness and feature a transformation at a critical temperature, referred to as the volume phase transition temperature. Whether this transformation occurs as a smooth or as a discontinuous one is still a matter of debate. This question can be addressed by studying individual microgels trapped in optical tweezers. For this aim, composite particles are obtained by decorating  Poly-N-isopropylacrylamide (pNIPAM) microgels with iron oxide nanocubes. These composites become self-heating when illuminated by the infrared trapping laser, performing hot Brownian motion within the trap. Above a certain laser power, a single decorated microgel features a volume phase transition that is discontinuous, while the usual continuous sigmoidal-like dependence is recovered after averaging over different microgels. The collective sigmoidal behavior enables the application of a power-to-temperature calibration and provides the effective drag coefficient of the self-heating microgels, thus establishing these composite particles as potential micro-thermometers and micro-heaters. Moreover, the self-heating microgels also exhibit an unexpected and intriguing bistability behavior above the critical temperature, probably due to partial collapses of the microgel. These results set the stage for further studies and the development of applications based on the hot Brownian motion of soft particles.     

锡酸四丁酯［［Sn(OBun)4］水解缩合实验研究

本文通过锡酸四丁酯［Sn(OBun)4］Sol-Gel过程中溶胶稳定性、acacH稳定剂作用、催化剂、pH影响及溶胶体系流变学测量,提出acacH的螯合中间体Sn(OBun)2(acac)2稳定机理、催化作用机理。流变学测量发现溶胶特性粘度［η］很好地符合近似线性模型,单体官能度f≈2.0,SnO2胶粒为近似线性分子链,分型维度D≈1.80,分形结构介于SAW链和无规高斯链之间,为螯合中间体Sn(OBun)2(acac)2的存在提供了实验证据。,In this paper,it was investigated experimentally that the SnO2 sol solution stability in teh sol-gel process derived by the precursor Tetrabutyiorthostannate (Sn(OBun)4:TBOS) was dramatically influenced by stability agent Acetylacetone (acacH),catalyst species,solution pH values.Based on the experimental observations, the sol stability role of agent acacH correlated to the chelate intermediate Sn(OBun)2(acac)2 as well as catalysis mechanismi were suggested through convincing discussion.It is revealed from rheological measurements of SnO2 sol systems that the relationship between the intrinsic viscosity ［η］ and the sol solution concentration of SnO2 sol particles is in good agreement with Quasi-Linear model of macromolecules,the functionality of modified monomer f is approximately equal to 2。0,and SnO2 sol particles show themselves as quasi-linear chain.On the other hand,its fractal dimension D≈1.80,and fractal structure stands between self-avoiding walk (SAW) chain and random Gussian chain.The evidence that the chelate intermediate Sn(OBun)2(acac)2 exists in the sol-gel process is presented by this study.     

Spontaneous Formation of Uniform Cell-Sized Microgels through Water/Water Phase Separation

In this study, a one-step method is discussed for producing uniform cell-sized microgels using glass capillaries filled with a binary polymer blend of polyethylene glycol (PEG) and gelatin. Upon decreasing temperature, phase separation of the PEG/gelatin blends and gelation of gelatin occur, and then the polymer blend forms linearly aligned, uniformly sized gelatin microgels in the glass capillary. When DNA is added to the polymer solution, gelatin microgels entrapping DNA are spontaneously formed, and the DNA prevents the coalescence of the microdroplets even at temperatures above the melting point. This novel method to form uniform cell-sized microgels may be applicable to other biopolymers. This method is expected to contribute to diverse materials science via biopolymer microgels and biophysics and synthetic biology through cellular models containing biopolymer gels.     

Poly (N-isopropylacrylamide) microgel-based assemblies for organic dye removal from water

Poly(N-isopropylacrylamide)-co-acrylic acid (pNIPAm-co-AAc) microgel assemblies (aggregates) were synthesized via polymerization of the cross-linker N,N'-methylenebisacrylamide (BIS) in the presence of microgels in solution. In this case, the microgels were entrapped in the polymerized cross-linker network. The aggregates were investigated for their ability to remove the organic, azo dye molecule 4-(2-hydroxy-1-napthylazo) benzenesulfonic acid sodium salt (Orange II) from water at both room and elevated temperatures. These results were compared with unaggregated microgels that were previously reported (Parasuraman, D.; Serpe, M. J. ACS. Appl. Mater. Interfaces 2011, 3, 2732.). It was found that the removal efficiency increased at elevated temperature, most likely due to the thermoresponsive nature of the pNIPAm-based aggregates, which expel water of solvation and deswell at higher temperature and reswell when they are cooled back to room temperature. Furthermore, increasing the number of cycles the aggregates are heated and cooled enhanced the percent removal of the dye from water. We also evaluated the effect of increasing cross-linker concentration on the removal efficiency, where we found the removal efficiency to increase with increasing cross-linker concentration in the aggregates. The maximum removal efficiency reached by the microgel aggregates at elevated temperatures was calculated to be 73.1%. This enhanced uptake is due to the presence of larger internal volume between the microgels in the aggregates, which the individual microgels lack. Control studies reveal that the structure and hydrophobicity of the aggregates lead to the enhanced uptake efficiencies and is not due to the presence of BIS alone. We determined that aggregates leak 75.6% of the dye that was originally removed from solution. The removal of Orange II by the aggregates at room temperature was fit by a Langmuir sorption isotherm.