Stimuli responsive polymers can undergo drastic changes in properties by responding to subtle changes in the environment. One specific type is thermoresponsive polymers, which are soluble in water but rapidly precipitate when heated to a specific temperature. The lower bound of this phase change is called the lower critical solubility temperature (LCST). Typically an LCST of lower than room temperature is targeted. This project focuses on synthesizing terminally functionalized thermosensitive polymers that allow for the grafting natural polysaccharides. This is particularly interesting because grafting natural polysaccharides such as hyaluronic acid onto the polymer forms a hybrid polymer that retains properties of both the synthetic and natural polymers. This can potentially form thermosensitive hydrogels that can release drugs in a controlled manner. Norbornene (NB) derivatives, all difunctionalized at the 2 and 3 carbons, were used as the monomers to control of the polymer architecture enabling the size and polarity to be easily controlled. The polymers were synthesized using ring opening metathesis polymerization with Grubbs’ 1stgeneration catalyst. The target LCST was a max of 25 oC. Polymers of different molecular weights with various monomers were synthesized to optimize the LCST. A homopolymer of NB functionalized with methyl carboxylate (NBDMC), a homopolymer of NB functionalized with triethylene glycol (NBTEG), and a copolymer of both species were explored. The polymerizations were terminated with 4-penten-1-ol. A variety of terminating agents were studied to find the optimal terminating agent for grafting the polysaccharide. The polymerization of NBDMC achieved a Mn of 12000 g/mol and was not soluble in phosphate buffer solution. The homopolymer of NBTEG achieved Mn’s of 35,000 and 14,000 and an LCST of 27 oC and 28 oC respectively. The copolymer consisted of a 2:1 ratio of NBTEG: NBDMC. This achieved a Mn of 30,000 and an LCST of 17 oC. The polymers were characterized via 400 MHz 1H NMR, gel permeation chromatography, dynamic light scattering, and TLC.

Synthesis of thermosensitive copolymers for the modification of polysaccharides

2019 Spring National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.