THE INFLUENCE OF ALKYLENE SPACERS ON CONFORMATIONAL AND THERMAL-PROPERTIES OF POLY(ARYL METHACRYLATES)

The effect of introducing alkylene spacers on the thermal and conforma tional properties of poly(aryl methacrylates) has been studied. Poly(2 -phenylethyl-1-methacrylate) (PPEMA) and poly(4-phenylbutyl-1-methacry late) (PPBMA) samples of narrow polydispersities and covering a very b road range of molecular weights were produced by free radical solution polymerization, followed by fractionation. These materials were studi ed by a combination of differential scanning calorimetry, light scatte ring, and viscometry measurements to allow evaluation of their glass t ransition temperatures (T(g)) and characteristic ratios (C(infinity)). These results are compared with literature data available for poly(ph enyl methacrylate) (PPMA), which has no alkylene spacer, and poly(benz yl methacrylate) (PBMA), which has a methylene spacer. A progressive d ecrease in T(infinity) is observed as the length of the alkylene space r is increased, reflecting the enhancement of side group (local) flexi bility. C(infinity) decreases substantially on going from PPMA to PBMA but then increases on going to PPEMA and PPBMA. This behavior is attr ibuted to the fact that while side group flexibility increases for the materials with longer alkylene spacers, and this would be expected to decrease C(infinity), the side group size is progressively increasing . Larger side groups generally increase C(infinity) of polymethacrylat es. Thus the observed C(infinity) behavior for these polymers reflects both the size and flexibility of the substituents. (C) 1994 John Wile y & Sons, Inc.