【作者】 陈荣；

【导师】 黄定海；

【作者基本信息】 天津大学 ， 材料学， 2012， 硕士

【摘要】 在科学和技术领域,研究纳米受限效应会对聚合物的平衡和动态性能产生的影响非常重要。本文用原子力显微镜(AFM)研究了旋转涂膜法制得吸附于云母片表面的聚苯乙烯(pS)纳米颗粒的形貌和尺寸及反浸润现象,还利用差示扫描量热仪(DSC)研究了快速蒸发法制得的PS单链或寡链纳米粒子的玻璃化转变现象。AFM对吸附于云母片表面的PS纳米颗粒的研究发现,在旋转涂膜法制备纳米颗粒的过程中,起初,分子链是以“簇状”聚集体的形式存在,随着旋涂时间的增加,这些聚集体在离心力的作用下逐渐分离或者被甩出云母片基质表面,慢慢消失,最终形成均匀分散的纳米颗粒。纳米颗粒的尺寸随着相对分子量的增加而增加。退火后的PS纳米颗粒发生了反浸润现象,其高度均发生不同程度的增加,颗粒高度的分布也变宽了。退火之后的样品与退火之前的样品相比,云母片表面出现了更多小的纳米颗粒,通过对这些纳米颗粒尺寸的测量,并与理论计算值对比,发现这些纳米颗粒为单分子链纳米颗粒。相对分子量越高的单链纳米颗粒,退火后高度增加越多,但将高度进行归一化处理后,发现尽管三个分子量的单链纳米颗粒高度变化不同,但是分子链收缩的程度是相同的,即PS单分子链在云母片表面已经达到平衡态。DSC对单链或寡链PS纳米粒子的玻璃化转变研究发现,PS的分子量越高,其玻璃化转变发生的温度越高,玻璃化转变温度(Tg)与分子量的倒数的关系基本符合Flory-Fox方程。不同分子量的PS纳米粒子的Tg均发生不同程度的下降,分子量越高,Tg下降的程度越大,这是由于快速蒸发法获得PS纳米粒子较本体PS的分子链缠结程度大大降低了,分子链缠结的减少促进了分子链段的运动,从而Tg会降低。通过熔融和重新溶解两种方法,这些试样的Tg均发生明显升高,说明分子链重新贯穿又产生新的缠结。更多还原

【Abstract】 In numerous scientific and technological fields, a fundamental understanding of the influence of nanoconfinement effects on the equilibrium and dynamic properties of polymeric materials proves to be of importance. Nanoparticles of polystyrene (PS) with different molecular weights adsorbed on mica substrates were prepared by spin coating from extremely dilute solutions, and dimensions and dewetting phenomenon of these samples were characterized by atomic force microscopy (AFM). Isolated single- or pauci-chain PS nanoparticles were obtained by fast evaporation from dilute solutions, and the glass transition phenomenon of these samples was characterized by differential scanning calorimeter (DSC).The AFM investigation on the PS nanoparticles adsorbed on mica showed that in the formation of nanoparticles, the PS molecules gathered in large clusters at the early stage, then the aggregates were separated or spun off, and more and more particles emerged, finally the clusters vanished and the particles formed on the substrate. The dimensions of the particles increased with molecular weight. The nanoparticles dewetted after annealing and the particle-height was elevated and the distribution was broadened. Numerous small particles appeared newly on the mica substrate after annealing. The volumes of these particles measured by AFM and the calculated volumes were in reasonable agreement, suggesting that the new-particles contained only one polymer chain. The higher the molecular weight of single-chain particle, the height increased more after annealing. After the height value were normalized, the extents of the chain contractions were the same, indicating PS single chains had reached equilibrium on mica, although height changes of single chains of three molecular weights were different.The DSC investigation on the PS nanoparticles obtained by fast evaporation method showed that the higher the molecular weight of PS, the glass transition happened at the higher temperature. The relationship between Tg and reciprocal of molecular weight coincided basically with Flory-Fox equation. Tgs of different molecular weight PS nanoparticles were decreased with different degrees, the higher molecular weight, the greater the degree of Tg declined. This was because that the degree of topological entanglements of PS by rapid evaporation method reduced greatly, which promoted the movements of chain segments, thus Tg was decreased. Through the melting or redissolving method, Tgs of these samples rised which showed that chains interlocked and formed new topological entanglements.更多还原