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Polymer Classification: Stereospecificity01:26

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Polymerization generates chiral centers along the entire backbone of a polymer chain. Accordingly, the stereochemistry of the substituent group has a significant effect on polymer properties. Polymers formed from monosubstituted alkene monomers feature chiral carbons at every alternate position in the polymer backbone. Relative to the predominant orientation of substituents at the adjacent chiral carbons, the polymer can exist in three different configurations: isotactic, syndiotactic, and...
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Unlike ionic or small covalent molecules, polymers do not form crystalline solids due to the diffusion limitations of their long-chain structures. However, polymers contain microscopic crystalline domains separated by amorphous domains.
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The introduction of polyesters has brought major development to the textile industry. The wrinkle-free behavior of polyester blends has eliminated the need for starching and ironing clothes.
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Esters can be hydrolyzed to carboxylic acids under acidic or basic conditions. Base-promoted hydrolysis of esters is a nucleophilic acyl substitution reaction in which esters react with an aqueous base, followed by an acid to give carboxylic acids. This reaction is also known as saponification because it forms the basis for making soaps from fats.
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Copolymers are the products obtained from the polymerization of multiple monomer species. So, in a polymer chain itself, there can be multiple repeating units that come from different monomers. The process of synthesizing a polymer from different monomer species is called copolymerization. When two monomers are involved, the polymer is known as a bipolymer. Polymers with three and four monomers are termed terpolymers and quaterpolymers, respectively. Figure 1 depicts the copolymerization of...
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The cationic polymerization mechanism consists of three steps: initiation, propagation, and termination. In the initiation step of the polymerization process, the π bond of a monomer gets protonated by the Lewis acid catalyst, which is formed from boron trifluoride and water. The protonation of the π bond generates a carbocation stabilized by the electron‐donating group. In the propagation step, the π bond of the second monomer acts as a nucleophile and attacks the...
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含有硫酸盐的共聚合物的结晶行为

Zhiyong Li1,2, Yongjing Chu1, Qing Huang1,2

  • 1State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620, China.

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概括

将硫酸盐组添加到阴离子可染聚 (CDP) 中会使结晶变得复杂,使得生产稳定的材料变得更加困难. 增加的硫酸盐含量降低了结晶温度,并阻碍了分子链堆叠,影响了材料特性.

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离子聚合物的离子聚合物.非同热结晶的非同热结晶.同酸-5-硫酸盐是一种同酸-5-硫酸盐.酸硫酸共聚的使用方法

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科学领域:

  • 聚合物科学 聚合物科学
  • 材料科学 材料科学 材料科学
  • 结晶运动学 结晶运动学

背景情况:

  • 由于复杂的结晶行为,阴离子可染聚 (CDP) 生产面临挑战.
  • 极性硫酸盐组影响了CDP的稳定性和加工特性.

研究的目的:

  • 为了研究不同硫酸盐群含量CDP的非异热结晶行为.
  • 了解同酸-5-硫酸 (SIPA) 对CDP结晶动力学和热性质的影响.

主要方法:

  • 通过SIPA,PTA和EG的单步养合成的共聚合物.
  • 使用差分扫描热量计 (DSC) 分析的非异热结晶.
  • 使用Jeziorny,Ozawa和Mo方程建模的结晶动力学;通过基辛格方程确定的激活能量.

主要成果:

  • 增加SIPA含量降低了结晶温度并增强了分子链放松.
  • 在低冷却速率 (2.5-5°C/分钟) 观察到的转移稳定的晶体和双峰.
  • 由于硫酸盐聚合的增加,冷结晶的峰值出现在较高的冷却速率 (10-20°C/分钟) 上.
  • 核密度,生长率和结晶的激活能量随着SIPA含量增加而下降.

结论:

  • SIPA含量显著影响CDP结晶行为,导致复杂的热过渡.
  • 硫酸盐组的离子聚合在改变链流动性和晶体形成方面发挥着至关重要的作用.
  • 更高的SIPA含量使得CDP结晶变得更加困难,影响加工稳定性和材料性能.