Release Time:2019-03-09  Hits:

Indexed by: Journal Papers

Date of Publication: 2016-01-01

Journal: RSC ADVANCES

Included Journals: SCIE

Volume: 6

Issue: 36

Page Number: 30320-30329

ISSN: 2046-2069

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 H-1 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 (eta(0)), enhanced complex modulus (G*) and increased complex viscosity (eta*). 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 (Delta 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,M-arm) than the total M-n.