Effect of network connectivity on the mechanical and transport properties of block copolymer gels

Abstract

Establishing the independent tunability of transport and mechanical properties in polymer gels would significantly contribute to their implementation as transdermal drug delivery media, among other things. The work conducted herein uses facile changes in the formulation of physically crosslinked styrenic ABA/AB block copolymer organogels to alter their mechanical properties independently from the mass transport of an internally-loaded nanocarrier. Such independent tunability is made possible by altering the relative amounts of ABA triblock and AB diblock copolymers while holding total copolymer concentration fixed. Specifically, three series of gels each with a fixed total copolymer concentration (10, 20, or 30 wt%) comprised of varying triblock copolymer concentration are studied. Small angle x-ray scattering confirms that, at the nanoscale, only gel network connectivity changes within each series, while mechanical and release experiments show that increasing network connectivity leads to significant growth of gel moduli, but little change in nanocarrier release rate.

Decoupling of Mechanical and Transport Properties in Organogels via Solvent Variation

“…The values of φ PS for each gel batch are calculated from known information, namely φ PS = f S × w SEBS (ρ S /ρ g ) where f S is the fraction of polystyrene in SEBS, w SEBS is the SEBS concentration in the gel, and ρ S and ρ g are the densities of polystyrene and the gel, respectively. As a result, G c and G e are the only fitting parameters used to describe stress-stretch data with the STN model and the fitted model represents data well up to λ zz ≈ 4 as has been noted in previous studies [17,19,21]. Furthermore, the values of G c and G e determined through fitting match the observations discussed above.…”

Recent progress in polymer hydrogel bioadhesives

“…Hydrogel-based transdermal drug delivery patches are widely used for transdermal delivery of various drugs. 138 Nishizawa et al 139 reported the application of solid polymer-based ionically conductive microneedles (PMN) in iontophoresis, which was a technology that promotes transdermal molecular transmission through the skin through direct current (Figure 14A). Ionic conductive PMN significantly reduced the transdermal resistance by partially destroying the stratum corneum, and the transdermal electroosmotic flow (EOF) from anode to cathode was generated by modification with hydrogel containing sulfonate group.…”

“…The released drug directly enters the local surrounding tissues or blood through the diffusion process. Hydrogel‐based transdermal drug delivery patches are widely used for transdermal delivery of various drugs 138 . Nishizawa et al 139 reported the application of solid polymer‐based ionically conductive microneedles (PMN) in iontophoresis, which was a technology that promotes transdermal molecular transmission through the skin through direct current (Figure 14A).…”

Temperature- and strain-dependent transient microstructure and rheological responses of endblock-associated triblock gels of different block lengths in a midblock selective solvent

“…Also, the triblock polymers considered are mostly thermoplastics; therefore, these gels are often referred to as thermoplastic elastomeric gels. The thermo-mechanical properties of these gels have been shown to be tuned by temperature, 6,15,18,19,23,25 polymer concentration, 6,21,23,26,27 length of A-and B-blocks, 7,28,29 choice of solvent, 16 inclusion of homopolymer, 9 and nanoparticles. 15 Because of the tunability of properties in such a diverse way, these gels have potential applications in ballistics, 25 tissue surrogates, 30 comfort and healthcare products like shoe soles and prosthetics, 31,32 gelcasting, 33 and soft robotics.…”