Cleavage of the Graft Bonds in PVDF-g-St Films by Boiling Xylene Extraction and the Determination of the Molecular Weight of the Graft Chains.

Chen Chen,Seko Seko

doi:10.3390/polym11071098

Abstract

To determine the molecular weight of graft chains in grafted films, the polystyrene graft chains of PVDF–g–St films synthesized by a pre-irradiation graft method are cleaved and separated by boiling xylene extraction. The analysis of the extracted material and the residual films by FTIR, nuclear magnetic resonance (NMR), and gel permeation chromatography (GPC) analyses indicates that most graft chains are removed from the PVDF–g–St films within 72 h of extraction time. Furthermore, the molecular weight of the residual films decreases quickly within 8 h of extraction and then remains virtually unchanged up to 72 h after extraction time. The degradation is due to the cleavage of graft bonds, which is mainly driven by the thermal degradation and the swelling of graft chains in solution. This allows determination of the molecular weight of graft chains by GPC analysis of the extracted material. The results indicate that the PVDF–g–St prepared in this study has the structure where one or two graft chains hang from each PVDF backbone.

Highlights

In contrast to photo-induced and chemical reagent-induced graft polymerization, radiation-induced graft polymerization can introduce graft chains on the surface and in the interior of solid materials, since the radiation can penetrate throughout the materials, thereby allowing a more uniform of radicals [1,2,3]
We aimed to investigate the cleavage of graft chains from grafted films using poly(vinylidene difluoride) (PVDF) as the backbones and polystyrene as graft chains, from which styrene-grafted PVDF (PVDF–g–St) films were prepared via a pre-irradiation grafting method [37]
PVDF–g–St film with a high degree of grafting of 91.8% was prepared by a pre-irradiation grafting method

Summary

Introduction

In contrast to photo-induced and chemical reagent-induced graft polymerization, radiation-induced graft polymerization can introduce graft chains on the surface and in the interior of solid materials, since the radiation can penetrate throughout the materials, thereby allowing a more uniform of radicals [1,2,3]. A hydrophilic monomer can be grafted onto a hydrophobic backbone [6,7,8,9], and an ionic monomer can be grafted onto an insulating film [10,11,12] Due to these versatile advantages, the radiation grafting has been used to modify existing films, fibers, and particles for applications such as ion-conductive membranes [13,14,15,16,17,18], adsorbents [19,20,21], sensor materials [9], and compatibilizers for polymer blends [22]. This radiation grafting is a “graft from” process in which free radicals that are produced on the backbones by irradiation initiated the polymerization of graft chains, forming C–C chemical bonds between graft chains and backbones, namely graft bonds [23,24,25]

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Conclusion