The Mechanism of Chain Growth during Synthesizing Aromatic Liquid Crystalline Polyester by Step-wise Melt-polymerization

Hua-qin Yang; Jun Kuang; Dong-hao Deng; Wen-le Zhou; Ying-cheng Li

doi:10.11777/j.issn1000-3304.2025.24296

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The Mechanism of Chain Growth during Synthesizing Aromatic Liquid Crystalline Polyester by Step-wise Melt-polymerization

Research Article | 更新时间：2025-06-17

- The Mechanism of Chain Growth during Synthesizing Aromatic Liquid Crystalline Polyester by Step-wise Melt-polymerization
- Acta Polymerica Sinica Vol. 56, Issue 5, Pages: 810-821(2025)
- 作者机构：
  
  中石化(上海)石油化工研究院有限公司上海 201208
- 作者简介：
  
  Ying-cheng Li, E-mail: liyc.sshy@sinopec.com
- 基金信息：
- DOI：10.11777/j.issn1000-3304.2025.24296
  CLC：
- CSTR：32057.14.GFZXB.2025.7367
- Received：14 December 2024，
  
  Accepted：19 February 2025，
  
  Published Online：01 April 2025，
  
  Published：20 May 2025
- 稿件说明：
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杨华琴, 况军, 邓东浩, 周文乐, 李应成. 逐步升温熔融聚合制备液晶聚酯过程中链增长机制的研究. 高分子学报, 2025, 56(5), 810-821

Yang, H. Q.; Kuang, J.; Deng, D. H.; Zhou, W. L.; Li, Y. C. The mechanism of chain growth during synthesizing aromatic liquid crystalline polyester by step-wise melt-polymerization. Acta Polymerica Sinica, 2025, 56(5), 810-821
杨华琴, 况军, 邓东浩, 周文乐, 李应成. 逐步升温熔融聚合制备液晶聚酯过程中链增长机制的研究. 高分子学报, 2025, 56(5), 810-821 DOI： 10.11777/j.issn1000-3304.2025.24296. CSTR： 32057.14.GFZXB.2025.7367.

Yang, H. Q.; Kuang, J.; Deng, D. H.; Zhou, W. L.; Li, Y. C. The mechanism of chain growth during synthesizing aromatic liquid crystalline polyester by step-wise melt-polymerization. Acta Polymerica Sinica, 2025, 56(5), 810-821 DOI： 10.11777/j.issn1000-3304.2025.24296. CSTR： 32057.14.GFZXB.2025.7367.

摘要

基于4-乙酰氧基苯甲酸(ABA)、2-乙酰氧基-6-萘甲酸(ANA) 2种共聚单体，探索了逐步熔融聚合反应过程中聚合组分随反应程度的变化关系，以及聚合反应温度对聚合物链段增长影响. 发现聚合反应初期(反应温度≤280 ℃)，聚合反应主要发生于各聚合反应单体的端基乙酰氧基与羧基之间以“头尾”相连的方式进行链增长，为酸解反应机理. 随着聚合反应程度增大，聚合反应体系逐渐形成双组分，在DSC测试中呈现出与热历史无关的双熔融峰，低熔融峰分布于270~278 ℃，高熔融峰分布于290~292 ℃. 在聚合反应后期，当反应温度为300 ℃时，聚合产物仍旧呈现双熔融峰. 而当聚合反应温度进一步升高至320 ℃时，聚合物进行链增长的同时发生了聚合物链段序列结构的无规化，促使了聚合体系由双峰转变为单峰分布，这主要是由于高温聚合反应条件下聚合物链间发生了酯交换反应.

Abstract

The chain-growth mechanism is discussed during synthesizing aromatic liquid crystalline polyester by step-wise melt-polymerization of ABA/ANA. At the initial stage of polymerization (polymerization temperature ≤280 ℃)

the 'head-to-tail' chain-growth procedure between the ca

rboxyl and acetoxy groups

known as acidolysis mechanism

is promoted showing the decreasing peak area of the acetoxy and carboxylic acid groups

while an increasing peak area of the ester group in the spectra of FTIR measurements of the polymeric components. Interestingly

two different melting temperatures

independence of the heating history

are observed by DSC scanning

with the increasing extent of polymerization. The lower temperature is in the range of 270-278 ℃ and the higher temperature is in range of 290-292 ℃

which suggests two polymeric components were formed during the polymerization. Furthermore

with the elevated polymerization temperature up to 300 ℃

the polymer chains propagate following the same mechanism as "head-to-tail". Meanwhile

the products keep showing two melting temperatures from the DSC scanning. However

by increasing the polymerization temperature to 320 ℃

the product shows the highest proportion of alternatively diad sequence by

C-NMR measurement and one melting temperature from the DSC scanning

which suggests that the randomization of the diad sequence and the transition of two polymeric components to uniformed product are accelerated. This is due to the transesterification between the polymer chains promoted by the increased polymerization temperature.

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references

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