Thermal properties of poly(neopentylmethacrylate) thin films deposited via solventless, radical initiated chemical vapor deposition

This paper investigates the thermal properties of thin films of poly(neopentylmethacrylate) (PnPMA) deposited via solventless, radical initiated chemical vapor deposition (iCVD). The effects of monomer to initiator molar ratio (M/I) on deposition kinetics, thermal properties and composition of the film were investigated. The molecular weight and conversion of PnPMA were observed to increase with increasing initiator concentration. Thermal properties of the film stabilized when annealed to 150 °C which was attributed to removal of short-chain molecules acting as “plasticizers”. Gel-permeation chromatography (GPC) studies and non-linear regression analysis of GPC data confirmed these results. M/I had no significant effect on the thermal stability of iCVD PnPMA and we hypothesize that this behavior is primarily due to weak bond linkages formed during polymer chain termination. The activation energy for the final thermal degradation stage of iCVD PnPMA was similar to that of anionically polymerized PnPMA, indicating that the iCVD polymer at this point was primarily composed of stable polymers that degrade through random chain scission.