Simmi Abrol

Studies on microgels. 5. Synthesis of microgels via living free radical polymerisation

Statistical and star microgels of t-butylstyrene-1,4-divinylbenzene (TBS-DVB) have been synthesized via living free radical polymerization using tetramethylpiperidin-1-oxyl (TEMPO) as a trapping agent. The alkoxyamines 1 and 2 were used as initiators to prepare statistical and star microgels, respectively. The molecular weight of the resulting microgels was determined by size exclusion chromatography with an on-line multi-angle laser light scattering (MALLS) instrument. It has been found that living free radical polymerization provides a much better control over the formation of statistical microgels than traditional free radical polymerization and can be used successfully for the synthesis of star microgels.

Studies on microgels: 4. The effect of solvent on the synthesis of t-butylstyrene-divinylbenzene microgels by anionic polymerization

t-Butylstyrene-1,4-divinylbenzene (TBS-DVB) microgels were synthesized by the arm first living anionic polymerization technique using two different solvents, heptane, a good solvent for poly(TBS) arms only and tetrahydrofuran (THF), a good solvent for both the arms and the poly(t-butylstyrene-co-4-vinylstyrene) block copolymer formed initially before crosslinking. The polymerizations were carried out using t-butyllithium as an initiator. The resulting microgels were characterised by size exclusion chromatography with an on-line multi angle laser light scattering instrument. In the polar solvent THF, much better control of the molecular weight of the microgels was observed. It is suggested that the mechanism of microgel formation is influenced by the solvent. Micelle formation is favoured in the case of heptane, which is a poor solvent for 4-vinylstyrene blocks.