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I. Thermal reconstruction of modified poly(chlorotrifluoroethylene) surfaces. II. Controlled chlorination of poly(ethylene) surfaces
Abstract
The thermal reconstruction (80-110$\sp\circ$C) of surface-modified films of poly(chlorotrifluoroethylene) (PCTFE) was studied by contact angle and x-ray photoelectron spectroscopy. The modified surfaces studied, synthesized via the reaction of PCTFE with lithium reagents, were PCTFE-TMO (containing a 10 A thick modified layer of dimethyl-oxazoline functionality), PCTFE-COOH (produced by hydrolysis of PCTFE-TMO), PCTFE-OH (30 A and 1100 A thick modified layers), and PCTFE-OC(O)CH$\sb3$, PCTFE-OC(O)CF$\sb3$, PCTFE-OSiMe$\sb3$, and PCTFE-OC(O)(CF$\sb2$)$\sb3$CF$\sb3$ (produced by reaction of 30 A-modified PCTFE-OH). Two reorganization processes are evident--one occurs in PCTFE-TMO and PCTFE-OH (30 A) for which changes are observed both by contact angle and XPS; migration of PCTFE units into the outer 10 A is proposed. Another process is evident in the reconstruction of PCTFE-OC(O)CH$\sb3$ and PCTFE-OH (1150 A) for which only a contact angle change is observed; repeat units do not measureably migrate and rotation is proposed. The heterogeneous (gas-solid) reaction of polyethylene films with chlorine gas was studied with the goal of confining the chlorination to the surface (outer $\sim$100 A) of the film. The effect of chlorine concentration, light intensity, and reaction time on the depth of chlorination (thickness of the modified layer) and extent of chlorination (density of chlorine substitution on the PE chain) was studied by XPS, ATR-IR, TIR, and gravimetric analysis. Chlorination with 1 atm. Cl$\sb2$ in the dark gave a low extent of substitution ($\sim$1 Cl per 9 C after 22 h) although the reaction proceeded deeply into the film. Chlorination with 1 atm. Cl$\sb2$ under UV or visible light gave more highly chlorinated surfaces ($\sim$1 Cl per C in 2 min.) and the reaction occurred more surface-selectively. Chlorination with low chlorine pressures (2-50 mm) was used to prepare samples with very thin ($<$100 A thick) chlorinated layers. A variety of reactions of the chlorinated (and brominated) polyethylene surfaces were attempted in order to assess the feasibility of using the surface-confined alkyl halides as a reactive handle for the synthesis of other modified polyethylene surfaces. Although the halogenated surfaces could be partially dehydrohalogenated (and the resulting double bonds could be brominated or hydroborated and oxidized) substitution reactions were unsuccessful.
Subject Area
Polymer chemistry
Recommended Citation
Cross, Elisa Martina, "I. Thermal reconstruction of modified poly(chlorotrifluoroethylene) surfaces. II. Controlled chlorination of poly(ethylene) surfaces" (1990). Doctoral Dissertations Available from Proquest. AAI9110120.
https://scholarworks.umass.edu/dissertations/AAI9110120