GLASS-TRANSITION OF STEREOREGULAR POLY(METHYL METHACRYLATE) AT INTERFACES

The glass transition temperature (T-g) of layers of stereoregular poly (methyl methacrylate) (PMMA) spin-cast on silicon and aluminum surface s has been investigated by ellipsometry. The interfacial specific inte ractions were highlighted and quantified by infrared reflection absorp tion spectroscopy. It was found that depending on PMMA tacticity, a st rong correlation exists between the density of the polymer/surface int eractions and the T-g of that polymer at the interface. Indeed, i-PMMA with a large density of interfacial interactions increases its T-g at the interface whereas s-PMMA with a lower value of bonded segments ex hibits a T-g depression. It is suggested that a certain level of inter facial interactions associated with an increase of density of the laye r will compensate for the increase of mobility resulting from a reduct ion of the entanglement density or a segregation of chain ends at an i nterface.