Reversible Complexation of Iminophenylboronates with Mono- and Dihydroxy Methacrylate Monomers and Their Polymerization at Low Temperature by Photoinduced ATRP in One Pot

The unique ability of boronic acids to form reversible covalent linkages to 1,2- and 1,3-diols creating boronate ester rings and the pH-sensitiveness of their dissociation have stimulated the development of boron containing polymers having phenylboronate moieties intended to be detached by competitive binding of sugars. Typically, they are synthesized by postpolymerization reactions on hydroxyfunctional polymers, which cannot guarantee a quantitative functionalization, or from monomers containing the phenylboronate moiety synthesized through multiple reaction/separation/purification steps. A handy strategy for the synthesis of monomers containing an iminophenylboronate (IPB) side-chain moiety derived from glycerol monomethacrylate (GMA) or 2-hydroxyethyl methacrylate (HEMA) and their polymerization in one pot is presented, which solves these issues and is flexible enough to be extended to a variety of hydroxy-functional monomers. First, a family of IPB methacrylates was synthesized through complexation of the hydroxyl moieties of GMA/HEMA with formylphenylboronic acid and a series of primary aromatic amines of increasing bulkiness ((S)-(-)-alpha-methylbenzylamine, (R)-(+)-1-(2-naphthyl)ethylamine, tritylamine, and 4-tritylaniline). They were subsequently polymerized by classical or UV-photoinduced ATRP at 0 degrees C, in DMF or DMF/toluene mixtures and with 1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA), (+)-sparteine, or 4,4'-dinonyl-2,2'-dipyridyl (dNbpy) as ATRP ligands. Poly(IPB methacrylate)s fully functionalized with IPB side-chain moieties, as verified by 2D-NMR spectroscopy, were competitive decomplexed against catechol, as followed by isothermal titration calorimetry and SEC measurements, releasing the highly hydrophilic pGMA or pHEMA backbone. Poly(IPB methacrylate)s were highly syndiotactic (rr = 74.9-79.7% for pHEMAs and 70.7-75.5% for pGMAs). The IPB-complex pathway strategy could easily be extended to the one-pot syntheses of block or random copolymers of hydrophilic hydroxy-functionalized monomers (besides HEMA or GMA) with hydrophobic macroinitiators or comonomers, which normally require a time-consuming protection/deprotection of the hydroxyl group(s) in separated steps.