A new class of degradable polymers is obtained from a diene monomer and molecular oxygen as the starting materials via a highly controlled radical copolymerization process. We now report the regiospecific copolymerization of a tetrasubstituted ethylene monomer with oxygen. Theoretical calculations support the highly selective propagations observed during the polymerization. The key steps are the regiospecific reactions of a peroxy radical to diene monomers and an allyl radical to molecular oxygen. The well-controlled molecular structure of the resulting polymer leads to the aldehyde-free degradation products during degradation by various stimuli, such as heating.

We have fabricated polyperoxides as new kinds of environment-friendly and degradable polymers using 1,3-diene compounds and oxygen as the starting comonomers under mild temperature and pressure conditions. They degrade in a radical chain mechanism by various stimuli; for example, degradation induced by physical (heating or irradiation), chemical (redox), and biochemical (enzymatic) stimuli.

We have fabricated degradable polyperoxides (PP) consisting of well-controlled 5,4-repeating units using various sorbic acid derivatives and molecular oxygen by an alternating radical copolymerization process. The PP obtained from the sorbic esters decompose via a radical chain reaction mechanism, leading to the formation of controlled low-molecular-weight products. In contrast, PP from some amide derivatives include an irregular chain structure, resulting in a more complicated degradation behavior. The theoretical calculations account for the selectivity in the two-step regiospecific propagation depending on the monomer structure. We have demonstrated the synthesis of functional PP based on two methods: one is the copolymerization of functional diene monomers with oxygen, and the other is the polymer reaction of PP including an azide group with a functional alcohol.

Water-soluble polyperoxides (PPs) as a new type of degradable and polymeric material were synthesized by the radical alternating copolymerization of sorbic derivatives containing a tetra(ethylene oxide) unit in the ester group using molecular oxygen. The obtained PPs showed a lower critical solution temperature (LCST)-type phase separation, and the transition temperature decreased according to the content of the hydrophobic ester group in the PPs. The PPs formed nanoaggregates with a diameter of 250-370 nm in water under the LCST. These PP aggregates were revealed to include 1-anilinonaphthalene-8-sulfonic acid as the fluorescence probe and epirubicin as the anticancer drug in their hydrophobic compartment. We evaluated the cytotoxicity and cellular uptake of the PPs in order to test their ability as a carrier used for the delivery of anticancer drugs. The cell viability in the presence of the PPs was comparable to those for the other biodegradable polymers, and epirubicin was taken up into the A549 efficiently with the PPs via an endocytosis mechanism.

Summary: A new kind of degradable gel was prepared by radical copolymerization of vinyl sorbate (VS) with molecular oxygen. A soluble and linear copolymer was produced at the initial stage of the polymerization and the ratio of the gel fraction was rapidly increased in the process of polymerization. An analysis of the polymerization by near infrared (NIR) spectroscopy strongly suggests that the conjugated diene group is much more reactive than the vinyl ester group. The degradation of an insoluble part (VS‐gel) was investigated by thermogravimetric (TG) and differential thermal analyses (DTA). Thermal degradation exothermically occurred around 110 °C. The weight loss of the gel was simultaneously observed. The VS‐gels obtained from polymerizations at various monomer concentrations had different physical properties, but similar degradation properties. The higher the VS monomer concentration in the feed, the lower the swelling ratio of the obtained gels due to an increase in a crosslinking density. The degradation of the VS‐gel under several stimuli other than heating was also investigated.