丙烯酰胺-苯乙烯双亲嵌段共聚物水溶液的粘度性能

STUDY ON RHEOLOGICAL BEHAVIOR OF AMPHIPHILIC BLOCK POLYMEROF ACRYLAMID-STYRENE

通过改变丙烯酰胺 (AM)与苯乙烯 (St)两单体的投料比 ,在微乳液介质中制备了分子组成系列变化的丙烯酰胺 苯乙烯双亲嵌段共聚物 (PAM b PSt) ,使用旋转粘度计测定了共聚物水溶液的表观粘度 ,详细考察了共聚物浓度、共聚物链结构、剪切速率、盐度及温度等因素对共聚物水溶液表观粘度的影响规律 .研究结果表明 ,由于PAM b PSt分子链中的PSt疏水嵌段链段之间具有强的疏水缔合作用 ,导致其具有独特的流变性能 .当共聚物水溶液的浓度高于某一临界值后 ,疏水缔合作用以分子间的缔合为主 ,大分子链之间会形成动态物理交联网络 ,增大了流体力学体积 ,使PAM b PSt水溶液可产生良好的增稠性能 ;疏水缔合作用是一吸热过程 ,升高温度有利于分子间的缔合 ,因此PAM b PSt水溶液具有良好的耐温性 ;聚合物水溶液中盐类物质的存在 ,会增强溶剂的极性 ,有利于分子间的缔合 ,使PAM b PSt水溶液具有良好的耐盐性 .

Amphiphilic block copolymers have many unique physical and chemical properties, especially stronger self-assembling ability, because of amphiphilic property and microphase separation of their molecules. In this investigation, the amphiphilic block copolymers of acrylamide(AM) and styrene(St) were prepared in microemulsion medium. One series of copolymers PAM-b-PSt was synthesized by changing the feed ratio under remaining other copolymerization conditions invariable. The apparent viscosity of the aqueous solutions of copolymers samples were measured using a rotational rheometer. The effects of various factors on apparent viscosity,such as concentration of polymer, composition of copolymer, shear rate, temperature and salt concentration, were investigated in detail. The studying results show that there is strong hydrophobic interaction between the block suctions of PSt in the macromolecules of PAM-b-PSt, so that stronger intermolecular hydrophobic associations are formed in aqueous solution and above a critical polymer concentration (about 0.2%, wt%). The intermolecular association leads to network structures and the hydrodynamic size of chains is increased, so the Amphiphilic block copolymer PAM-b-PSt exhibits good thickening property. The another reason leads to good thickening property of PAM-b-PSt is that introducing of phenyl groups of styrene significantly enhanced the viscosity. Besides, under increasing shear, the physical links between chains are disrupted, but recover with decreasing shear, and also the associations are enhanced by the application of shear. The reversibility of the rheological property can to avoid the irreversible mechanical degradation. Therefore, the reversible association/dissociation process gives rise to particular rheological behaviors for PAM-b-PSt. Because hydrophobic association is endothermic,the intermolecular association is favoured by increasing the temperature,and so PAM-b-PSt has the withstanding temperature property. The containing of salt in aqueous solution of polymer can increase the polarity of the solvent, and the effect favoured the intermolecular association. As a consequence, the solution of the block copolymer PAM-b-PSt has salt resistance. Above described excellent properties of amphiphilic block copolymer PAM-b-PSt will leads to its wide commercial application.