Reversible Photomodulation of the Swelling of Poly(oligo(ethylene glycol) methacrylate) Thermoresponsive Polymer Brushes

Abstract

Photothermoresponsive polymer brushes were synthesized by coupling azobenzene derivatives to oligo(ethylene glycol) methacrylate (OEGMA) based copolymer brushes grown from silicon substrates. Varying the length and chemical ending of the lateral chains (using different OEGMA comonomers) afforded a collection of thermoresponsive copolymer brushes with predetermined fraction of hydroxyl side groups. These pendent hydroxyl functions were subsequently used to anchor the photochromic modules onto the brushes via classical activation/coupling chemistry, albeit in modest to moderate yields depending on the brush composition, thickness and grafting density. The extent of swelling of the functionalized brushes in water could be reversibly modulated by photoisomerization of the azobenzene motifs, even though the amplitude of the observed variation remained small. Decreasing the grafting density of the brush afforded improved photoresponse possibly through decreased steric crowding between the chains, facilitating azobenzene coupling and isomerization in the confined system.

Meso‐ and Microscopic Motions in Photoresponsive Liquid Crystalline Polymer Films

“…If the lateral polymer density is sufficiently high, surface brushes are formed, which provide unique molecular orientations and properties . With respect to photoresponsive polymer brushes, there are a number of examples for SI polymerizations of photochromic monomers such as spiropyrans and azobenzenes . They exhibit fascinating smart responsive functions; however, this review will not touch on them and focuses only to LC brush systems.…”

“…[ 39,40 ] With respect to photoresponsive polymer brushes, there are a number of examples for SI polymerizations of photochromic monomers such as spiropyrans [41][42][43][44] and azobenzenes. [45][46][47] They exhibit fascinating smart responsive functions; however, this review will not touch on them and focuses only to LC brush systems.…”

Precision PEGylated Polymers Obtained by Sequence‐Controlled Copolymerization and Postpolymerization Modification

“…[23] Monomer 5 bears a photoswitchable azobenzene group, which is also of interest for tuning the hydrophilic-hydrophobic balance of PEGbased polymers. [24] Monomers 7 and 8 contain reactive functionalities that can be used after polymerization for local chain modification. [19,25] The NMP copolymerization of a large excess of 3 (20 molar equivalents as compared to the initiator) with discrete amounts of N-substituted maleimides (an equimolar amount with respect to the initiator) enabled sequence control.…”

Effects of Thickness and Grafting Density on the Activity of Polymer‐Brush‐Immobilized Tris(triazolyl) Copper(I) Catalysts

“…PHEMA brushes were grown on freshly activated Si chips and functionalized using a method described previously (Scheme ) 9h. 26 Briefly, the stepwise synthetic procedure started with the coating of single‐crystal Si wafers (1×1 cm 2 ) with an initiator monolayer. Following surface‐initiated atom transfer radical polymerization (SI‐ATRP), the pendant hydroxyl functions of the brushes were activated using N , N ′‐disuccinimidyl carbonate (DSC)/Et 3 N and coupled with TTMA derivative 4 (Experimental Section).…”