Photocaged pendent thiol polymer brush surfaces for postpolymerization modifications via thiol‐click chemistry

Abstract

In this work, a postpolymerization surface modification approach is reported that provides pendent thiol functionality along the polymer brush backbone using the photolabile protection chemistry of both o-nitrobenzyl and p-methoxyphenacyl thioethers. Poly(2-hydroxyethyl methacrylate) (pHEMA) brushes were synthesized via surface-initiated atom transfer radical polymerization, after which the pHEMA hydroxyl groups were esterified with 3-(2-nitrobenzylthio)propanoic acid or 3-(2-(4-methoxyphenyl)-2-oxoethylthio)propanoic acid to provide the photolabile protected pendent thiols. Addressing the protecting groups with light not only affords spatial control of reactive thiol functionality but enables a plethora of thiol-mediated transformations with isocyanates and maleimides providing a modular route to create functional polymer surfaces. This concept was extended to block copolymer brush architectures enabling the modification of the chemical functionality of both the inner and outer blocks of the block copolymer surface.

Post‐Functionalization of Polymers via Orthogonal Ligation Chemistry

“…Polythiol copolymers were subsequently obtained by aminolysis of the xanthate protecting groups at ambient temperature. Patton and co‐workers156 equipped polymer brush backbones with photolabile o ‐nitrobenzyl and p ‐methoxyphenacyl thioethers for a post‐polymerization surface modification approach. Application of light affords spatial control of reactive thiol functionalities and enables thiol‐mediated transformations for functional polymer surfaces.…”

Thiol-Substituted Poly(2-oxazoline)s with Photolabile Protecting Groups—Tandem Network Formation by Light

“…The novel monomer 2-{2-[(2-nitrobenzyl) thio]ethyl}-4,5-dihydrooxazole ( 4 ), abbreviated NbMEtOxa, was prepared in four steps partially based on concepts from the literature (see Scheme 1 ) [ 45 ]. For the synthesis of 3-[(2-nitrobenzyl)thio] propanoic acid ( 1 ), the thiol group of mercaptopropionic acid was protected with o -nitrobenzyl bromide, according to reaction procedures published by Hensarling et al and Pauloehrl et al [ 46 , 47 ]. In the subsequent step, the carboxyl group was converted to the N -hydroxysuccinimide ester 2 and directly coupled with 2-chloroethylamine to yield amide 3 .…”

Protected thiol strategies in macromolecular design

“…Almost every functional group can be protected with a photo-labile protecting group and some excellent reviews have appeared on this subject [129][130][131]. A major advantage of photodeprotection methods is the possibility to generate the desired functional group with spatial and temporal control.…”