端羟基化聚苯乙烯的表面性质

Surface Properties of Hydroxy-terminated Polystyrenes

利用Wilhelmy片技术和躺滴法研究了端羟基化聚苯乙烯的表面性质.结果表明,端羟基化对聚苯乙烯在空气面的接触角基本没有影响(89°),而在玻璃面的接触角则大大降低(66°),其降低幅度与分子量及分子量分布有关.这与动态接触角的测定结果基本一致,而且宽分子量分布的端羟基化聚苯乙烯的前进接触角(θa)随着温度的升高而降低,于40℃时达到最低值.而窄分子量分布样品的动态接触角基本不变.样品与不同温度水接触后表面接触角的变化也基本相似.DMA研究结果表明,样品损耗模量、储能模量和tanδ从40℃开始发生突变,刚好与接触角最低值的温度相对应.这是由于宽分子量分布样品中的较低分子量组分在表面聚集,导致表面分子具有较高的活动能力.接触角随温度的变化趋势可能是聚合物表面分子运动能力增加和结晶程度变化等因素综合作用的结果.

The surface properties of hydroxy-terminated polystyrenes were investigated by Wilhelmy plate technique and sessile drop method. The results show that the static contact angles for water on the air-side surface and the advancing contact angles of the films were almost the same as the unfunctionalized polymer. However, the contact angles on the glass-side surface and the receding contact angles were found to decrease greatly. At the same time, it was found that the molecular weight distribution（PDI） of the polymer was an important factor to affect the surface dynamic behavior of hydroxy-terminated polystyrene. The advancing contact angles of the film with bread PDI decrease with increasing of temperature, and reach a minimum at 40 ℃, whereas that of narrow PDI polymer have not been affected by temperature. The similar result was obtained by heating the film against water. DMA results show that the loss modulus, storage modulus and tanδ of PS—OH-1 began to change sharply at 40 ℃ at which the minimum of contact angle appeared. The reason may be attributed to the polymer molecules with lower molecular weight segregating to surface, which result in molecules in surface layer having a higher activity. We speculate that the observed results about the minimum contact angle at 40 ℃ are associated with the enhanced molecular freedom on surface and changes in bulk structure such as crystaUinity.