Viscoelastic Properties of Polymer Blends in Miscible and Immiscible States

研究了聚合物共混体系在1)混相和2)非混相状态下的粘弹性特性，并对其相分离范围进行了研究：1)在M_<PS>>>M_<PVME>的条件下，以混相状态下聚苯乙烯/聚乙烯醇/聚乙烯醇共混体系的零剪切粘度eta <s:1>和稳态柔度J_e作为PS （M_<PS>和ph_ <PS>）的分子量和组分的函数（M_<PS>和ph_ <PS>）。结果表明，在ph_ <PS><0.2的半稀区，聚合物共混物的eta <s:1>可以用与半稀聚合物溶液相同的标度规律来表示，J_e与聚合物溶液的J_e基本一致。2)以牛顿流体共混体系为模型，以硅油/液态树脂共混体系为模型，以聚二甲基硅氧烷/聚丁二烯共混体系为模型，在非混相状态下测定了聚合物共混体系的粘弹性。研究发现，如果减去组分聚合物的应力，这些共混物的剪应力和正应力差异可以用Doi和Ohta提出的织构材料理论很好地解释。3)在相分离温度附近，研究了具有近临界成分的PS/PVME共混物在稳定剪切流动中的粘弹性特性。结果表明，均相区黏度eta和柔度J_s与剪切速率的关系与均相区基本相同，但相分离区eta和J_s在低剪切速率下增强，当剪切速率高于各自的临界值时与均相区一致，表明剪切诱导均相化。

Viscoelastic properties of polymer blends were studied in 1) miscible and 2) immiscible states, and 3) a vicinity of phase separation as follows :1) zero-shear viscosity etaﾟ and steady-state compliance J_e of polystirene/poly(vinyl methylether)(PS/PVME) blends in the miscible state were measures as functions of the molecular weight and composition of PS (M_<PS> and phi_<PS>) in the condition that M_<PS>>>M_<PVME> where M_<PVME> is the molecular weight of PVME.It was found that the etaﾟ of the polymeer blends in the semidilute region where phi_<PS><0.2, can be expressed by the same scaling law as semidilute polymer solutions, and the J_e almost agrees with that of polymer solutions. 2) Viscoelastic properties of silicone oil/liquid resin blends as a model of Newtonian fluid mixtures and polydimethylsiloxane/polybutadiene blends as a model of polymer blends were measured in the immiscible state. It was found that the shear stresses and normal stress differences of these blends are well explained by the theory of textured materials presented by Doi and Ohta, if the stresses of the component polymers are subtracted. 3) Viscoelastic properties of PS/PVME blends with the nearly critical compositions in steady-shear flow were studied in the vicinity of phase separation temperature. It was found that the shear rate dependences of viscosity eta and compliance J_s in the homogeneous region are almost the same as those of homopolymers, but the eta and J_s in the phase-separated region are enhanced at low shear rates and become consistent with those in the homogeneous region, when the shear rates are higher than their respective critical values, implying shear-induced homogenization.