A Scaling Theory of the Competition between Interdiffusion and Cross-Linking at Polymer Interfaces

Abstract

We study theoretically situations where competition arises between an interdiffusion process and a cross-linking chemical reaction at interfaces between pieces of the same polymer material. An example of such a situation is observable in the formation of latex films, where, in the presence of a cross-linking additive, colloidal polymer particles initially in suspension come at contact as the solvent evaporates and, optimally, coalesce into a continuous coating. We considered the low cross-link density situation in a previous paper and presented a simple control parameter that determines the final state of the interface. In the present article, with the help of simple scaling arguments, we extend our description to higher cross-link densities. We provide predictions for the strength of the interface in different favorable and unfavorable regimes and discuss how it can be optimized.

Deformation and adhesion of a periodic soft–soft nanocomposite designed with structured polymer colloid particles

“…The closepacked particles deform into rhomboid dodecahedra to fill the available space (appearing like a honey-comb in two dimensions). Because the polymer has a very low T g , interdiffusion occurs readily when the particles come into contact at room temperature 11,12 . The ADH crosslinker reacts with the DAAM ketone groups slowly, thereby allowing interparticle interdiffusion to proceed initially, but eventually the crosslinking blocks any further diffusion, effectively freezing in place the original core-shell structure of the particles (Fig.…”

“…As a result the "classic" adhesive made from latex particles consists of a percolating network of entangled interfaces encapsulating microgelled particle cores. [10][11][12] Although empirical design rules adapted to specific materials are prevalent in the patent literature, fundamentally-based general design principles for soft adhesives are virtually nonexistent. The key reason for the lack of a design guideline is that adhesive debonding involves large-scale deformation of the adhesive itself, and only a careful control of the nonlinear large strain properties can lead to a knowledge-based design 13 .…”

Investigation of the effect of precoalescence or postcoalescence crosslinking on film formation, properties, and latex morphology

“…The crosslinked particles formed tough elastomeric films with high tensile strength and substantial elongation to break but with expected poor solvent resistance. Aradian et al 20 developed a theoretical mode to account for the competition between interdiffusion and crosslinking at polymer interfaces drawing upon the experimental work of Winnik and coworkers.…”

Characterization of Molecular Structure of Emulsion Acrylic Microgels: Exploring the Impact of Molar Mass on Coating Properties of Self-Cross-Linkable Latexes

“…The final coating is then formed by the coalescence of individual particles into a film. In order to obtain a macroscopically strong film, the polymer chains must interdiffuse at the interfaces between the particles [10,11]. This is, of course, not a problem for linear polymers of low glass transition temperature (T g ) but the coalescence of lightly crosslinked microgels results in interfaces that remain weaker than the particles and a lightly crosslinked network is not continuous, which typically leads to worse final coating properties [12].…”