In this study, we investigated the effects of the 4-hydroxybutyrate (4HB) content and sequence distribution of 3-hydroxy butyrate (3HB)-4HB chains on their non-isothermal crystallization behavior of biodegradable P(3HB-co-4HB). In addition, the effect of melt processing temperature on the crystallization was also examined. As a result, it was possible to control the 4HB content and the chain sequence such as the distribution of 3HB chain block, 4HB chain block, and 3HB-4HB random chain block in the copolymer depending on the fermentation conditions by bacteria. This difference in chain sequence distribution affected the non-isothermal crystallization behavior of P(3HB-co-4HB), and it was confirmed that the crystallization rate increased and the degree of crystallinity decreased as the 4HB chain increased. It was also found that increasing the melt processing temperature caused thermal decomposition of P(3HB-co-4HB), affecting non-isothermal crystallization behavior. This resulted in decreasing the crystallization of the 3HB-4HB random chain block and 4HB chain block while increasing the crystallization of the 3HB chain block.

본 연구는 생분해성 고분자인 poly(3-hydroxybutyrate-co-4-hydroxybutyrate(P(3HB-co-4HB))의 4HB 함량과 3HB-4HB 사슬 sequence distribution이 비등온 결정화 거동에 미치는 영향을 살펴보았다. 이와 함께 용융 가공온도가 이들 결정화에 미치는 영향도 함께 확인하였다. 연구 결과, 박테리아의 발효 조건에 따라 4HB 함량과 공중합체의 3HB block, 4HB block, 그리고 3HB-4HB random block 조절이 가능함을 알 수 있었다. 이러한 sequence distribution 차이는 P(3HB-co-4HB)의 비등온 결정화 거동에 영향을 주어 4HB 사슬 증가에 따라 결정화속도는 증가되며 결정화도는 감소됨을 확인하였다. 용융 가공온도 증가는 P(3HB-co-4HB)의 열분해를 초래하여 비등온 결정화 거동에 영향을 미쳐 3HB 사슬 block에 결정화는 증가시키는 반면, 4HB가 포함된 3HB-4HB 사슬 random block과 4HB 사슬 block의 결정화를 감소시킴을 확인하였다.

Keywords: poly(3-hydroxybutyrate-co-4-hydroxybutyrate), non-isothermal crystallization, chain sequence distribution, processing temperature, thermal degradation.