Abstract
The synthesis of macroinitiators containing diarylmethyl groups as anionic presursors at the termini of ethylene oligomers are described. These oligomers were then entrapped into a large excess of virgin high density polyethylene via a technique called entrapment functionalization. These anionic precursors are located mainly on the surface of polyethylene films which can be easily deprotonated by n-BuLi to generate diarylanions at the polyethylene film surface. Poly(tert-butyl acrylate) was grafted to polyethylene films using these initiators. Hydrolysis of poly(tert-butyl acrylate) grafted polyethylene films led to a poly(acrylic acid) grafted polyethylene surfaces. Characterization of the grafted films by surface selective techniques such as contact angle goniometry, X-ray photoelectron spectroscopy, and ATR-IR spectroscopy showed that grafting took place mainly on the surface of polyethylene film. Detailed spectroscopic studies of the ungrafted and grafted polyethylene surfaces containing fluorescently tagged diarylmethyl groups have demonstrated that the presence of surface grafts at a polyethylene surface determines the surface reactivity and accessibility. The solvent-dependent changes in reactivity of the grafted polyethylene surfaces or interfaces are consistent with the solubility characteristics of the grafted chains. In the case of poly(acrylic acid) grafted polyethylene films, the pH dependence for salvation of the graft and for the exposure of the underlying fluorophore resembled the pH behavior of a strong acid. This behavior was manifest in a sharp change in the salvation of the grafted polymer surface over a narrow pH range. This led to a significant and sudden change in the reactivity of pyrene functional groups at the base of the graft toward an aqueous phase fluorescence quencher.
Bandella, Ashok Krishangopal (1996). Synthesis and elaboration of polyethylene surfaces modified via anionic grafting chemistry. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1996 -THESIS -B355.