Combining ATRP and FRP Gels: Soft Gluing of Polymeric Materials for the Fabrication of Stackable Gels

Abstract

Stackable gels comprised of layers of dissimilar polymers were synthesized by combining conventional free radical polymerization (FRP) and atom transfer radical polymerization (ATRP) using two approaches: (i) polymerization of a pre-gel solution containing a monomer and cross-linker introduced on top of a previously prepared gel, and (ii) simultaneous polymerization of two immiscible pre-gel solutions remaining in contact. All permutations of FRP and ATRP yielded single-piece, connected, amphiphilic gels regardless of the order of polymerization. Furthermore, multi-layer ATRP gels combining different polymers were synthesized with the FRP layer as a gluing agent. A 10-layer amphiphilic stackable gel combining n-butyl methacrylate (BMA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA), and a 10-layer stackable gel combining BMA, DMAEMA and di(ethylene glycol) methyl ether methacrylate (PEO 2 MA) were synthesized. This patching method, combining conventional FRP gels with ATRP ones, offers an efficient path to the formation of complex stackable gel architectures.

Structurally Tailored and Engineered Macromolecular (STEM) Gels as Soft Elastomers and Hard/Soft Interfaces

“…Here, we describe how to achieve considerable spatiotemporal control over the STEM gels and thereby expand the field of photodriven additive manufacturing. − In particular, by employing photoinduced ATRP, − we demonstrate how the STEM gel can be transformed from a hard network to a soft elastomer by postsynthesis. We also show how to harness the STEM gels to create elastomers that contain both hard and soft domains and, thus, provide a new means of addressing the need for a single polymeric sample that contains mechanically distinct domains. − …”

Shape-Changing Tubular Hydrogels

“…Our method for preparing hybrid tubular gels is illustrated in Figure 1. This method was developed previously in our lab [1] and has been subsequently copied and extended by others [9,10]. The key to this method is to stack the pre-gel solutions when their viscosities are sufficiently high, so as to drastically minimize convective mixing between the solutions [1].…”

“…Moreover, we noted that current approaches to create novel hydrogels were mainly focused on tuning the chemical structure of the monomers used in gel synthesis [5,6]. In comparison, physical approaches to creating hybrid hydrogels have been relatively unexplored [7,8,9,10], and we have therefore focused our efforts in this direction.…”

Reversible Deactivation Radical Polymerization: State-of-the-Art in 2017

“…The parent network was initially designed via free radical copolymerization of different monomers, a crosslinker, and a photo-active dormant initiator/monomer (inimer) based on the radical photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (Irgacure 2959) with latent initiating sites for post-polymerization of secondary network. The secondary network was then generated through infiltration of monomers followed by activation under UV light resulting in materials spatially differentiated mechanical properties (200). Reversible covalent chemistry was also introduced to alter the topology of polymers, which often is an inalterable post-synthetic feature (Scheme 6) (201).…”