Adhesion promotion at a homopolymer–solid interface using random heteropolymers

Abstract

We investigate the potential uses for random heteropolymers ͑RHPs͒ as adhesion promoters between a homopolymer melt and a solid surface. We consider homopolymers of monomer ͑segment͒ type A which are naturally repelled from a solid surface. To this system we add RHPs with both A and B ͑attractive to the surface͒ type monomers to promote adhesion between the two incompatible substrates. We employ Monte Carlo simulations to investigate the effects of variations in the sequence statistics of the RHPs, amount of promoter added, and strength of the segmentsegment and segment-surface interaction parameters. Clearly, the parameter space in such a system is quite large, but we are able to describe, in a qualitative manner, the optimal parameters for adhesion promotion. The optimal set of parameters yield interfacial conformational statistics for the RHPs which have a relatively high adsorbed fraction and also long loops extending away from the surface that promote entanglements with the bulk homopolymer melt. In addition, we present qualitative evidence that the concentration of RHP segments per surface site plays an important role in determining the mechanism of failure ͑cohesive versus adhesive͒ at such an interface. Our results also provide the necessary input for future simulations in which the system may be strained to the limit of fracture.

Random Copolymer Adsorption at the Polymer Melt/Substrate Interface: Effect of Substrate Type

“…Simmons and Chakraborty have published Monte Carlo simulations of surfaces segregation in a system similar to oursa random copolymer mixed in a homopolymer. The homopolymer consisted only of A units while the copolymer contained both A and B units.…”

Conformation of Adsorbed Random Copolymers: A Solid-State NMR and FTIR-PAS Study

“…Above this maximum, an increasing sticker concentration decreases the fracture energy due to cohesive failure . In regards to the relation of chain conformation to this behavior, Gutman and Chakraborty argued that a sticker concentration higher than optimal leads to the formation of a flat polymer layer, giving rise to a second diffuse interface between the near-surface chains and those further away from the solid surface 7a. They propose that the locus of failure is at this second interface.…”

“…Poly(ethylene- co -acrylic acid) is commonly used as an adhesion promoter for polyethylene coatings on metal and paper surfaces. Simmons and Chakraborty have theoretically investigated the use of random heteropolymers as adhesion promoters between a homopolymer melt and a solid surface 7b. The conformation of the random heteropolymer as a function of coverage and fraction of adsorbed segments was examined.…”

“…Gong et al showed that a critical concentration of carboxylic acid sticker groups is required for optimal chain connectivity near the surface and a maximum in the fracture energy . Theoretical studies of adsorbed random copolymers predict that the maximum fracture energy is associated with the chain conformation at the interface . It was recently reported that the bonding of fatty acids and acrylic acid copolymers to alumina can be enhanced by pretreating the surface with zirconium alkoxides .…”

Physical association of polymers with nanotubes

“…As with other surfaces,5, 6 the interfacial bonding of physically adsorbed polymers on CNTs may fail adhesively or cohesively, and one should therefore tailor the polymer as to address both of these issues. While oligomers and surfactants are expected to fail either adhesively (weak CNT‐polymer interactions) or cohesively (strong CNT‐polymer interactions), long polymer chains and, in particular, copolymer chains might be able to address both these failures 7…”