Rheological properties and crystallization behavior of comb-like graft poly(l-lactide): influences of graft length and graft density. Issue 36 (24th March 2016)

• Record Type: Journal Article
• Authors: Leng, Xuefei; Wei, Zhiyong; Bian, Yufei; Ren, Yingying; Wang, Yurong; Wang, Qinyi; Li, Yang
• Is Part Of: RSC advances. Volume 6:Issue 36(2016)
• Page Start: 30320
• Page End: 30329
• Publication Date: 2016-03-24
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/c6ra02697d
• Languages: English
• ISSNs: 2046-2069

Abstract

Abstract : Radius growth rate of spherulites ( G ) versus crystallization temperature ( T c ) for graft PLLA with different graft density and graft length. Abstract : Three series of narrowly dispersed comb-like graft poly(l -lactide) (PLLA) with controlled graft length and graft density have been facilely synthesized and characterized. The structural information was determined by means of 1 H NMR, GPC, and viscometry, demonstrating the well-defined grafted structure. The effects of grafting parameters on rheological properties, thermal and crystallization behaviors were investigated systematically to illustrate the structure–property relationships. By the analysis of the rheological behavior, the increase of graft length and graft density can both lead to an elevated value of zero-viscosity ( η 0 ), enhanced complex modulus ( G *) and increased complex viscosity ( η *). Comparatively, graft density contributes more to the improvement of rheological properties than graft length does. For thermal properties, DSC results show that the glass transition temperature ( T g ), the melting temperature ( T m ) and the crystallization enthalpy (Δ H m ) of graft PLLA increase with the chain length and decrease with the graft density. Furthermore, spherulite morphologies and growth rates were studied by polarized microscopy (POM), and the observation revealed a remarkable improvement of radius growth rate of the spherulites ( G ) when graft density increased. The results indicate that G depends more on the molecular weight of each arm ( M n, arm ) than the total M n .