Thermally Initiated Trans-esterification in Poly(ε-caprolactone) and Its Dependence on Molecular Weight

• Published in: Journal of polymers and the environment Vol. 22; no. 4; pp. 479 - 487
• Main Authors: Pal, Jit, Sanwaria, Sunita, Choudhary, Aman, Thakur, Kapeesh, Nandan, Bhanu, Srivastava, Rajiv K.
• Format: Journal Article
• Language: English
• Published: Boston Springer US 01-12-2014; Springer; Springer Nature B.V
• Subjects: Aliphatic compounds; Applied sciences; Biodegradable materials; Biodegradation; Biomedical engineering; Bioplastics; Chemical modifications; Chemical reactions; Chemical reactions and properties; Chemistry; Chemistry and Materials Science; Degradation; Environmental Chemistry; Environmental Engineering/Biotechnology; Exact sciences and technology; Industrial Chemistry/Chemical Engineering; Materials Science; Molecular weight; Networks; Organic polymers; Original Paper; Physicochemistry of polymers; Polyester resins; Polymer Sciences; Polymers; Reduction; Degradation; Poly(ε-caprolactone); Heat; Trans-esterification; Molecular weight; Intramolecular reaction; Reaction product; Mechanical properties; Competitive reaction; Tensile property; Thermal reaction; Transesterification; Experimental study; Lactone polymer; Reaction mechanism; Intermolecular reaction; Polycaprolactone
• ISSN: 1566-2543; 1572-8919; 1572-8900
• DOI: 10.1007/s10924-014-0669-4

Biodegradability and biocompatibility of poly(ε-caprolactone) (PCL) are the prime properties which advanced the use of this polymer in fields of tissue engineering and biomedicals. Being an aliphatic polyester, PCL is prone to undergo trans-esterification which is one of the mechanisms reported for its degradation besides being used in making its copolymers. Trans-esterification occurs both, inter- and intra-molecularly and in this work we report that the mechanism of trans-esterification depends on the molecular weight of the polymer when it is subjected to 160 °C for time up to 24 h. For low molecular weight PCL (M
p
 = 10,000 g/mol) inter-molecular trans-esterification is the predominant mechanism while for the high molecular weight PCL (M
p
 = 80,000 g/mol) it is intra-molecular. A mid molecular weight PCL (M
p
 = 43,000 g/mol) showed presence of both, inter- as well as intra-molecular trans-esterification, when heated at 160 °C for 24 h. A decrease in relative crystallinity for all the samples showed reduction in crystalline component of the polymer confirming occurrence of trans-esterification at chosen conditions. An increase in tensile strength and modulus is observed after treatment at 160 °C for 24 h due to formation of more entangled network of polymer chains as a result of trans-esterification reactions.