Enolate‐initiated dispersion polymerisation

Abstract

We wish to report the first use of initiation by enolate ions in anionic dispersion polymerisation. The system that we have employed is of the type which has frequently been referred to in the literature in recent years as "group-transfer polymerisation" ' 3 'I. This unfortunate name arose from a misconception of the mechanism of certain anionic polymerisations initiated by enolate ions; in fact, reactions of this type had been known for many years3-8), and this fact is now recognised9). Enolate initiation has proved to be very useful for conducting anionic polymerisation at relatively high temperatures, and we are now able to report that its use can readily be extended to dispersion polymerisation.Dispersion polymerisation is a process in which reaction is performed in a solvent medium which is miscible with the monomer but not with the resulting polymer; the system contains a surface-active agent which stabilises the polymer particles against coalescence'0,''). In our experiments, the stabiliser was a block copolymer of the structure polystyrene-block-poly(ethene-co-propene) (PS-PEP); this has been used with success in other dispersion polymerisations ' ' 3 13). Experimental part a) MaterialsMethyl methacrylate was washed twice with aqueous KOH, twice with water, and then stored over Na2S0, for about 5 h. After filtratioa, the monomer was treated with CaH, , filtered again, and stored overnight in contact with a 4 A molecular sieve. It was subsequently passed through a column of basic alumina, and again stored over molecular sieves.Neptune was purified by distilling over CaH, , and storing over molecular sieves. (I-Methoxy-2-methyl-I-propenyloxy)trimethylsilane (MTS) (Aldrich) was used without further purification.Tetrabutylammonium fluoride (TBAF) (Aldrich) was used as a solution in dry tetrahydrofuran (0,1275 mol/L).The steric stabiliser, polystyrene-block-poly(ethene-co-propene) (PS-PEP), manufactured by the Shell Chemical Company under the trade-mark Kraton G1701 (34 wt.-To PS, mass-average molar mass Mi, = 1,05 . LO5 g . mol -I ) was purified by twice dissolving in toluene, precipitating into methanol, and drying overnight in a vacuum oven.

Block Copolymers in Emulsion and Dispersion Polymerization

“…In a similar way, Jenkins and co-workers [227] polymerized MMA in nheptane by group transfer polymerization in the presence of PS-PEP as steric stabilizer.…”

Thermosensitive copolymer synthesized by controlled living radical polymerization: Phase behavior of diblock copolymers of poly(N‐isopropyl acrylamide) families

“…For example, the monomer used in the second polymerization should have an electron affinity that larger than or equal to the monomer used in the first polymerization . On the other hand, controlled living radical polymerization can improve the previous limitations …”

“…The polydispersity index (PDI) of a polymer synthesized by general radical polymerization cannot be controlled. Ionic (or chain‐growth) polymerization and group‐transfer polymerization can synthesize a polymer with a controlled molecular weight and PDI, but the reaction conditions are strict . For example, a small amount of impurities may affect the reaction to have chain transfer or reaction termination, and the selection of monomers is also limited.…”

A splice site mutation confirms the role of LPIN2 in Majeed syndrome

“…Dispersion polymerization is a unique and effective single step process for producing monodisperse polymer particles in the size range of 1–15 μm 5–7. Usually, dispersion polymerization is carried out using the conventional free‐radical method, although nonaqueous dispersion polymerizations such as living anionic8 and group transfer9 polymerizations have been explored to provide polymer dispersity with controlled morphology.…”