Crosslinking of Pressure-Sensitive Adhesives with Polymer-Grafted Nanoparticles

Abstract

Nanocomposite filler particles provide multiple routes to mechanically reinforce pressure-sensitive adhesives (PSAs), as their large surface area to volume ratios provide a means of effectively crosslinking multiple polymer chains. A major advancement could therefore be enabled by the design of a particle architecture that forms multiple physical and chemical interactions with the surrounding polymer matrix, while simultaneously ensuring particle dispersion and preventing particle aggregation. Understanding how such multivalent interactions between a nanoparticle crosslinking point and the PSA polymer affect material mechanical performance would provide both useful scientific knowledge on the mechanical structure−property relationships in polymer composites, as well as a new route to synthesizing useful PSA materials. Herein, we report the use of polymer-grafted nanoparticles (PGNPs) composed of poly(nbutyl acrylate-co-acrylic acid) chains grafted to SiO 2 nanoparticle (NP) surfaces to cohesively reinforce PSA films against shear stress without compromising their adhesive properties. The use of acrylic acid-decorated PGNPs allows for ionic crosslinking via metal salt coordination to be used in conjunction with physical entanglement, yielding 33% greater shear resistance and up to 3-fold longer holding times under static load. In addition, the effects of material parameters such as PGNP/crosslinker loading, polymer graft length, and core nanoparticle size on mechanical properties are also explored, providing insights into the use of PGNPs for the rational design of polymer composite-based PSAs.

Hierarchically Structured Nanocomposites via a “Systems Materials Science” Approach

“…To circumvent this limitation, we have developed polymer grafted nanoparticles (PGNPs) that possess short brushes that can be cross-linked postprocessing (Figure B). − , The use of cross-links instead of chain entanglement to impart mechanical strength enables filler loadings as high as 57 vol % without sacrificing mechanical properties . These PGNPs can use different types of cross-linking moieties (for example, anhydrides and amides), and can be processed into conformal films and arbitrarily shaped 3D objects through hot pressing, compression molding, extrusion, or vacuum forming. ,, Nevertheless, while these cross-linked PGNPs possess homogeneously distributed fillers, they lack long-range organization.…”

“…One of the first steps toward a systems materials design concept for hierarchical composites is therefore to elucidate appropriate building blocks that have structural features that can be intentionally programmed at these different length scales. Our group has tackled this challenge by developing a suite of polymer-grafted nanoparticles that are inherently composite architectures, containing both rigid inorganic cores and soft polymeric brushes. − These designs provide a major advantage in the investigation of “systems” approaches to materials synthesis by using molecular and nanoscale handles to manipulate assembly during the formation of higher-order structures, and also allowing nanoscale design features to alter supramolecular behavior. By exploiting biomolecular recognition, supramolecular chemistry, nanoparticle synthesis, and processing methods, we have begun to outline a potential pathway toward a “systems materials science” approach to developing new polymer composites.…”

Topology and Dynamic Regulations of Comb-like Polymers as Strong Adhesives

“…Strong adhesives with high load-bearing capabilities can provide both adhesive bonding to substrate surfaces and cohesive bonding throughout the bulk material. As a result, they are able to withstand static loads and frequent loading–unloading conditions, which is beneficial for enhancing safety and extending service life in the wood glue, cement nails, electronic devices, and automotive industries. − From the perspective of adhesive applications, strong adhesives required to transfer force between adhered substrates usually have several characteristics: (1) a low elastic modulus, which allows for solid contact and strong bonding with the substrates; (2) an elastic character at a low frequency, which can resist flow during debonding; and (3) a notable degree of viscoelasticity, which provides enough energy dissipation during debonding when external stress is applied. , …”

Comparative Mechanical Study of Pressure Sensitive Adhesives over Aluminium Substrates for Industrial Applications

“…It is important to note that the resistance of this type of adhesives not only depends on their nature but also on the degree of crosslinking of the polymer chains [ 10 ]. Non-crosslinked polymers are also widely used as PSAs, the resistance of which is improved by the introduction of fillers whose particles form a three-dimensional network [ 15 , 16 ]. Likewise, the use of nanotubes as filler particles in the adhesive matrix provides this three-dimensional network, which improves the mechanical properties of PSAs [ 15 , 16 ].…”

“…Non-crosslinked polymers are also widely used as PSAs, the resistance of which is improved by the introduction of fillers whose particles form a three-dimensional network [ 15 , 16 ]. Likewise, the use of nanotubes as filler particles in the adhesive matrix provides this three-dimensional network, which improves the mechanical properties of PSAs [ 15 , 16 ]. Among the groups of PSAs mentioned above, the most employed in the industrial sector are acrylic-based materials, with numerous families differing in the polymerization process (emulsion, solution, hot melt, or radiation curing) [ 17 , 18 , 19 ].…”