Graft polymerization

Abstract: This thesis is focused on morphological aspects of polymericsubstrates used in graft polymerization. Morphological changesof selected polymer systems were investigated in the virginstate and after irradiation, during the progress of graftpolymerization, in the final grafted state and duringsubsequent degradation.Preparation of a substrate with a pre-determined morphologyis advantageous in graft polymerization and copolymerization isan effective tool. Copolymerization of 1,5-dioxepan-2-one (DXO)with lactones (ε-caprolactone, CL andδ-valerolactone, VL) and lactide (L-lactide, L-LA)generated copolymers in which both the crystallinity and themelting temperature decreased as the content of DXO wasincreased. The copolymers of DXO and CL or VL showed inclusionof DXO units within the crystals, whereas the DXO units wereentirely excluded from the PLLA crystals.The progression of the grafting front is a dynamicinteraction of several parameters where morphology has aprofound effect. As the grafting front progressed into the PEfilm substrate the crystallinity and lamellar dimensions werechanged over continuously transforming grafting stages, due tothe differences in morphology obtained after pre-irradiation inair or argon and the disintegration of the morphology by thegrafted macroradicals. The samples pre-irradiated in an argonatmosphere had a significantly higher extent of crosslinks thanthose irradiated in air, and this affected the graftingprogress and consequently the deterioration of themorphology.When the graft polymerization has terminated, the finalmorphology is settled. In order to achieve predeterminedmorphologies, it is essential to direct the parametersaffecting the final morphology. Commercial PCL was able tograft polymerize to high final graft yields, depending on theatmosphere during irradiation, and the dose and concentrationof inhibitor. These final graft yields were accompanied bylarge variations in crystallinity where PCL samplespre-irradiated in air exhibited higher crystallinity over theentire range of dose and inhibitor concentration than PCLsamples pre-irradiated in argon.Degradation of surface-grafted PCL was primarily enhanced byirradiation which led to a notably reduced molecular weight,and to a lesser extent to improved permeation achieved by asurface layer of polyacrylamide (PAAm).Keywords: Morphology, Poly(ethylene),Poly(ε-caprolactone), Copolymers of DXO, Irradiation,Graft polymerization.