【作者】 王京；

【导师】 胡文兵；

【作者基本信息】 南京大学 ， 高分子化学与物理（专业学位）， 2015， 硕士

【摘要】 通过对比环形分子结晶性能,我们可以研究线形分子链端基对于结晶性能的影响。本文采用了商业化快速扫描量热仪Flash DSC 1对于不同分子量环形和线形聚己内酯(PCL)结晶和成核速率的研究。第一章我们介绍了,在绿色化学以及环境污染的大背景下,人们对于环保材料的需求越来越大。聚己内酯作为一个可以自然降解并且具有良好热稳定的高分子材料被人们所关注。从热力学角度可以很容易对聚己内酯物理性质进行研究。同时,随着合成水平的提高,不仅仅是线形聚己内酯可以被合成,环形的聚己内酯同样可以被合成出来,人们对于链拓扑结构对于高分子性能影响也越来越感兴趣。然而常规热分析仪很难观察到整个范围内结晶速率相对较快材料的结晶和成核性质。快速扫描量热仪的发展使得我们对于物质热力学研究范围更加宽广。因此,我们可以对聚己内酯从玻璃化转变到熔融的结晶和成核性质做一个系统的研究。第二章,我们简单的介绍了所要研究的环形和线形PCL的合成路线,以及其基本物理性质,比如分子量、多分散系数等。随后我们阐述了实验过程中的仪器性能以及基本操作,讲述了通过快速扫描量热仪Flash DSC1,以及等温结晶的半结晶和半成核时间的理论推导以及实验条件的确定。第三章,根据实验条件我们得到了环形和线形聚己内酯在-50℃到50℃范围内,不同温度下的半结晶和半成核时间的曲线图。通过对比,我们发现高温的时候短链环形分子要比线形分子结晶和成核速率快。这个和Muller教授之前的结果相一致。在低温的时候,我们观察到了环形和线形聚己内酯的半结晶时间有个交叉,这是由于它们之间的成核速率的改变有关,和后面的半成核时间曲线图相对应。同时低温的时候,线形聚己内酯的结晶速率要快于环形,我们认为这是由于线形分子提供了可以移动的端基使得短程扩散要快于环形。长链则表现出相似的结晶和成核速率,这个是因为环形长链的拓扑结构与线形逐渐接近的结果。中分子量的结果因为仪器限制,所以测量的结果并不是十分可靠。第四章是总结与展望。更多还原

【Abstract】 The role of chain ends and entanglements in the crystallization of linear polymers can be understood by comparing the mechanisms of crystallization to cyclic counterparts.We employed a commercially available chip-calorimeter(Flash DSCl)to compare the nucleation and overall crystallization rates between linear and cyclic poly(epsilon-caprolactones)(PCL)with two different molar masses.In Chapter 1,we introduced the background of environment pollution and green chemistry for the development of degradable polymeric materials.As an environment-biodegradable material,poly(epsilon-caprolactones)contain good thermal stability properties.With the development of synthetic technique,not only the linear PCL,but also the cyclic PCL can be produced.We can thus study about the influences of the ring topologic structure on the crystallization behaviors.However,the standard calorimetry instruments cannot meet all the demands of comparison.Hence,the fast-scan calorimetry has been employed to expand the comparison investigation.In summary,with this new technique,we have an opportunity to study the differences between cyclic and linear PCL on crystallization and nucleation behaviors from glass state or molten state.In Chapter 2,we introduced the synthetic path of cyclic and linear PCLs good for the comparable study.We have showed the basic factors of these two different kinds of materials,for instance molecular weight.After that,we showed the advanced instrument named as Flash DSC Ⅰ and its basic operation.We ensured the theoretical derivation and its experiment condition for obtaining the half-crystallization and half-nucleation times.In Chapter 3,according to the experiment condition we chose,we investigated the half-crystallization and half-nucleation times in the range from-50 ℃ to 50 ℃ for the cyclic and linear PCLs.Comparing in the results,we found cyclic PCL has faster crystallization and nucleation rates than the linear counterpart,which is consistent to the previous results reported by Prof.Muller’s group in the high temperature region.As for the low temperature,we observed that the crystallization rates of cyclic and linear PCLs have intersections,which are related to the nucleation rates.Also,linear PCL has a faster homogeneous nucleation rate that reveals short nature of linear chains at low temperatures,due to their higher mobility of free chain-ends.As for the long chains,cyclic PCL shows similar results as the linear counterpart.Due to the limit of the instrument,the cyclic and linear PCLs of middle molecular weight cannot get accurate results.In Chapter 4,we summarized conclusions above,and suggested subjects for future study.更多还原