Viscoelastic behavior of semidilute solutions of multisticker polymer chains
Viscoelastic behavior of semidilute solutions of multisticker polymer chains
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DOI：
10.1021/ma990999e
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发表时间：
1999-12-14
期刊：
影响因子：
5.5
通讯作者：
Candau, F
中科院分区：
文献类型：
--
作者：
Regalado, EJ;Selb, J;Candau, F
采用自由基胶束聚合技术制备了由水溶性聚丙烯酰胺组成的多黏贴聚合物链，该聚合物链由少量N，N-二己基丙烯酰胺进行疏水改性。该工艺得到了多嵌段共聚物，其中疏水嵌段的数量和长度可以通过改变表面活性剂与疏水物质的摩尔比来调节。采用稳态流动和振荡实验研究了不同分子量(M-w近似为4.2 × 10（4)-2.7 × 10(6)）、疏水含量（[H] = 0.5-2 mol %）和疏水嵌段长度（N-H = 1-7单位/嵌段）的共聚物半稀溶液的粘弹性行为。在半稀释范围内，零粘度eta(o) = f(C)曲线可以清楚地区分出两种不同的状态：第一种不纠缠状态，其中粘度增加速率强烈依赖于N-H和[H]；在第二种纠缠状态下，粘度遵循聚合物浓度的标度行为，指数接近4，无论[H]或N-H。线性粘弹性可以描述为(i)一个缓慢的松弛过程，其平台模量仅取决于聚合物浓度和（iii）其他更快的复杂松弛过程。在后一种情况下，结果可以用受阻重复模型很好地解释。
Multisticker polymer chains consisting of water-soluble polyacrylamides hydrophobically modified with low amounts of N,N-dihexylacrylamide have been prepared by a free radical micellar polymerization technique. This process gives multiblock copolymers in which the number and length of the hydrophobic blocks can be tuned by varying the surfactant over hydrophobe molar ratio. The viscoelastic behavior of semidilute solutions of various series of copolymers with variable molecular weights (M-w approximate to 4.2 x 10(4)-2.7 x 10(6)), hydrophobe contents ([H] = 0.5-2 mol %), and hydrophobic block lengths (N-H = 1-7 units per block) has been investigated as a function of polymer concentration, C, using steady-flow and oscillatory experiments. In the semidilute range, two different regimes can be clearly distinguished in the zero-sheer viscosity eta(o) = f(C) curves: a first unentangled regime where the viscosity increase rate strongly depends on N-H and [H]; a second entangled regime where the viscosity follows a scaling behavior of the polymer concentration with an exponent close to 4, whatever [H] or N-H. The linear viscoelasticity can be described by (i) a slow relaxation process with a plateau modulus that only depends on polymer concentration and (iii other faster complex relaxation processes. In the latter regime, the results can be quite well accounted for by a hindered reptation model.