EFFECT OF BLOCK-COPOLYMER DOPANTS AND ALKYLSILANE MONOLAYERS ON THE FRACTURE-TOUGHNESS OF POLYSTYRENE-GLASS INTERFACES

The asymmetric double cantilever beam fracture test has been used to s tudy the fracture toughness of polystyrene (PS)-glass interfaces reinf orced with poly(deuterostyrene-b-2 vinyl pyridine) (dPS-PVP) as a func tion of degree of polymerization of the blocks. The effect of modifyin g the glass substrate with various selfassembled monolayers is also de scribed. For the block copolymer with degrees of polymerization, N-dPS =656 and N-PVP = 46 (referred to as N-dPS - N-PVP or 656-46), located at the interface between glass and PS, the interface fails by chain sc ission at areal chain densities, Sigma, of the block copolymer below a critical value, Sigma. Above this value, e.g. Sigma > Sigma*, the in terface fails by crazing followed by chain scission. For the 656-46 di block copolymer, the transition is located at Sigma = 0.03 chains nm( -2), which results in a calculated force to break a C-C bond along the polymer backbone of approximately 2 x 10(-9)N. For the 800-870 dibloc k copolymer at the interface between glass and PS, failure occurs due to chain scission. Fracture of both the 656-46 and the 800-870 block c opolymers at the interface between (OTS) octadecyltrichlorosilane mono layer coated glass and PS is due to chain pulloff of the block copolym er from the OTS coated glass. Very little additional stress was transf erred across the interface, resulting in fracture tough nesses com par able to that of a PS-glass interface with no block copolymer added.