Retardation of Polymerization in Substituted Styrenes by Chelated Nitrophenols.

Abstract

The polymerization of vinyl monomers has been inhibited or retarded by many substances including quinoid, hydroquinoid, and nitrophenolic compounds; the terms "inhibition" and "retardation" are differentiated in this article according to the definitions given by Foord (27). A comparison is made of the behavior of these compounds, particularly the nitrophenolic compounds, as polymerization retarders, studying the effect of temperatures and chelation upon their relative efficiency. The temperature effect is important in the selection of an inhibitor (or retarder) because a compound suitable to prevent polymerization of a monomer at room temperature and at low concentration during storage does not necessarily prevent polymerization during distillation. This fact is especially true when hydroquinoid compounds are compared with nitrophenolic compounds, and/or sulfur is compared with phenolic compounds. Apparently, an inhibitor (or retarder) has a certain operable temperature range, and a higher temperature destroys the inhibitor by its reaction with a growing polymer chain, or by thermal decomposition. Therefore, the stabilizing effect produced by chelation would be important in the inhibition of monomer at higher temperatures. EXPERIMENTAL Apparatus. The polymerization bath and the constant temperature water bath were identical, consisting of a borosilicate glass battery jar 12 inches high and 12 inches in diameter, set

Synthesis and Characterization of Biodegradable HPMA-Oligolysine Copolymers for Improved Gene Delivery

“…Similar behavior was reported in another system where increasing the feed mol% of a comonomer with lower reactivity decreased the overall molecular weight of the resulting copolymer (32). The decrease in molecular weight with increasing mol% of peptide may also be attributed to the DNP label on the peptide, because it is known that DNP can act as a chain transfer agent during radical polymerization (33–34). The ability of DNP to accept radicals retards the polymerization, extending the time required for polymerization in the presence of DNP compared to a polymerization in the same conditions except without DNP (33).…”

“…The decrease in molecular weight with increasing mole percent of peptide may also be attributed to the DNP label on the peptide, because it is known that DNP can act as a chain transfer agent during radical polymerization , . The ability of DNP to accept radicals retards the polymerization, extending the time required for polymerization in the presence of DNP compared to a polymerization in the same conditions except without DNP . Thus, the copolymers synthesized at the higher mole percent of peptide will be retarded the most due to the presence of the highest concentration of DNP, and 48 h may not be long enough to extend the chains fully, resulting in lower molecular weights.…”