Synthesis and Spontaneous Polymerization of Oligo(ethylene glycol)-Conjugated Benzofulvene Macromonomers. A Polymer Brush Forming a Physical Hydrogel

Two methyl end-capped oligo(ethylene glycol) esters (1a,b) of benzofulvene derivative BF1 were synthesized and induced to polymerize spontaneously by solvent removal to give poly-1a,b showing both NMR and absorption/emission spectra very similar to those of poly-BF1. Poly-1a,b showed relatively high molecular weight and the tendency to depolymerize to a different degree as a function of the temperature in the presence of solvents, while they exhibited appreciable stability in the absence of solvent. Poly-1b, bearing a longer oligo(ethylene glycol) side chain, featured an amphiphilic character and interacted with a number of organic solvents to produce transparent gel aggregates, and with water to give a quite compact physical gel. Rheological studies performed on the hydrogel suggested strong gel characteristics and the combination of rheology and NMR transverse relaxation measurements allowed the pore size distribution in the hydrogel to be defined. Finally, biological studies performed with poly-1b solutions showed neither cytotoxicity nor cell viability impairment suggesting potential biocompatibility features for this polymer. In conclusion, poly-1b can be considered a promising polymer for the preparation of hydrogels potentially useful in a range of biological and biotechnological applications such as drug delivery, molecular recognition, biosensing, protein and DNA separation, micro- and nanofluidics, as well as tissue engineering.