Crystallization Of Poly(ε-carprolactone)-b-poly(L-lactide)Diblock Copolymers Induced By Oriented Polyethylene

Polymer crystallization is a process in which chains rearrange regularly. This process can be affected by many factors and one of the most is the chemical and physical property of the substrate. Poly(ε-carprolactone)(PCL) and poly(L-lactide)(PLLA) are both a kind of nature biodegradable semi-crystalline materials. However, lower glass-transition temperature of PCL and brittle property of PLLA inhibit their development and application. One way to overcome this shortage is to synthesize diblock copolymers of poly(ε-carprolactone)-b-poly(L-lactide)(PCL-PLLA), collaborating PCL and PLLA properties.PCL and PLLA homopolymer epitaxial crystallization on polyethylene (PE) had been investigated for many years. It has been certified in PCL/PE, c-axis of PCL is parallel to c-axis of PE; and in PLLA/PE, c-axis of PLLA is perpendicular to c-axis of PE. Nevertheless, the combination of PCL-PLLA/PE has not yet been explored. Here, we used polarized optical microscopy, transmission electron microscopy, infrared linear dichroism spectroscopy and etc. to study PCL-PLLA/PE epitaxial crystallization, and used Cerius2to simulate models. The results showed that oriented PE substrate can change morphology of PCL-PLLA and induced it to form oriented structures: c-axis of PCL is perpendicular to PE substrate, which is different from the homo-PCL. That indicated adding PLLA can disturb PCL’s orientation.In this thesis, different molecular weight was also considered. Fixed PCL as40K, change PLLA from5K,10K,20K,40K to60K. Particularly, as PLLA crystallize firstly, the former PLLA crystalline parts can inhibit crystallization of PCL. With the increase of PLLA molecular weight, this interference was enhanced and oriented crystalline behavior of PCL was even worse.All the above results showed that oriented PE substrate can induce PCL-PLLA to form oriented epitaxial crystalline and this behavior is connected with its molecular weight and block percentage. This work has successfully verified the conjecture that homo-and co-polymer are different in epitaxial crystallization, and provided new evidence or ideas to study its mechanism further.