The Role of Polymer Architecture in Strengthening Polymer−Polymer Interfaces:  A Comparison of Graft, Block, and Random Copolymers Containing Hydrogen-Bonding Moieties

Abstract

A series of styrene-d 8/4-hydroxystyrene graft and block copolymers has been prepared by “living” radical and anionic techniques for use in interfacial strengthening studies at the polystyrene/poly(2-vinylpyridine), PS/PVP, interface. The following copolymers in which A and B segments represent poly(styrene-d 8) and poly(4-hydroxystyrene), respectively, have been prepared: poly(A-graft-B), poly(B-graft-A), poly(B-block-A-block-B), poly(A-block-B-block-A-block-B-block-A). The poly(4-hydroxystyrene) segments were obtained by “living” radical polymerization of 4-acetoxystyrene or anionic polymerization of 4-methoxystyrene, followed by conversion to the phenolic derivative. In general, the amphiphilic copolymers when placed at the PS/PVP interface acted as interfacial reinforcers but were susceptible to the formation of microphases such as lamellae or micelles, and therefore the measured fracture toughness depended on both the copolymer/homopolymer interfacial strength and the toughness of the copolymer phase structure itself. The pentablock copolymer showed better strengthening behavior than the triblock copolymer especially at very low areal chain density. The strengthening ability of the graft copolymers was found to depend on the lengths of the polystyrene, PS, and poly(4-hydroxystyrene), PS(OH), segments. In both graft and block copolymers the PS(OH) segments were found to resist pull-out from the bulk PVP even at low degrees of polymerization (N PS(OH) = 29). The H-bonding interaction between the phenolic and pyridyl groups combined with the severe immiscibility of poly(4-hydroxystyrene) and polystyrene is the most likely cause for pull-out resistance.

The reinforcement of polystyrene and poly(methyl methacrylate) interfaces using alternating copolymers

“…In a separate study, PS/P(2VP) interfaces were also reinforced by multiblock copolymers composed of S and poly (4-hydroxystyrene). This system also demonstrated that the pentablock copolymer was a more effective interfacial modifier than the triblock copolymer, [11] in agreement with our recent results [4 -6,34] that suggest that blocky copolymers are the most effective interfacial strengtheners.…”

“…The effectiveness of random copolymers to reinforce polymers interfaces has also been widely investigated [11,12,15,21,22,[33][34][35][36][37][38] and was found to be dependent on the monomer composition [22]. In the case of PðS f -ran-MMA 12f Þ; where f is the monomer composition, the compositionally asymmetric P(S 0.7 -ran-MMA) displayed the greatest reinforcement of the PS/PMMA interface out of a range of P(S-ran-MMA) compositions studied [21].…”

Z. Guan, Control of polymer topology through late‐transition‐metal catalysis, J Polym Sci Part A: Polym Chem (2003), 41(22), 3680–3692

“…2,3 A significant amount of effort has been devoted to developing efficient methods for accurately controlling polymer topology and architecture with the aim of preparing polymeric materials with new properties. 4 Many concepts and synthetic approaches have been developed to prepare macromolecules with various architectures and topologies, including dendrimers [5][6][7][8] and hyperbranched polymers, 9 -15 supramolecular polymers, 16 -21 cylindrical and spherical polymers, [22][23][24] polymers having folded structures, [25][26][27] molecular wires, 28 -30 metal-core polymers, 31,32 and polymeric nanostructures.…”

Synthesis of polyethene–graft–polystyrene copolymers from linear polyethene-containing cyclopropane rings

“…In this respect, it is worth noting that graft copolymers are largely used for the compatibilization of immiscible polymer blends. [15][16][17][18][19][20][21] In the past decade, investigations on polymer blends have intensified significantly because they offer a convenient alternative to developing totally new polymers. Polymer blends can be tailored to meet the requirements of specific applications.…”