Other thermogelling polymers

Orthoester is the triether groups linked a carbon atom. Contrary to the ester that subject to acid-base catalyzed hydrolysis, orthoester is hydrolyzed faster under 

Thermogelling aqueous solutions of poly(ethylene glycol)-poly(ethyl-2-cyanoaerylate) (PEG-PEC) were reported (Fig. 13.10). Polycyanoacrylate is degraded by esterases to cyanoacryUc acid. The PEG-PEC diblock copolymer aqueous solution showed a sol-to-gel-to-sol transition as the temperature increased as well as the concentration increased, thus, forming a closed-loop gel domain in the phase diagram. 

Poly(N-(2-hydroxyproyl) methacrylamide (HPMAm)-oligolactate) (MW = 10-20 K Daltons) was linked to PEG (MW = 10 K Daltons) to show thermogelling polymer aqueous solution (Fig. 13.10). The gel modulus eould be controlled by the molecular weight of the poly(HPMAm-oligolactate) (Fig. 

Poly(N-isopropyl acrylamide) (PNIPAAm) is one of the most widely studied temperature sensitive polymers that undergoes clear solution to precipitation. However, its nonbiodegradabihty and concern for residual monomer toxicity limit the biomedical applications. To improve the problems, biodegradable 

11 Structure of poly(HPMAm-oligolactate)-PEG-poly(HPMAm-oligolactate). 

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Besides chitosan, naturally derived polymers such as hyaluronic acid can be chanically modified to form thermogels. For example, copolymers of NlPAAm and aCTylic add N-hydroxysuccinimide were first synthesized via free radical polymerization and then bonded to amine-functionalized hyaluronic acid (HA) to form a thermogelling polymer [53]. Other types of naturally derived polymers such as methyl cellulose have well-documented thermogelUng effect as well [54]. 

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