Carbohydrate/monomer complexes in aqueous polymerizations: Methylated-beta-cyclodextrin mediated aqueous polymerization of hydrophobic methacrylic monomers

Hydrophobic methacrylic monomers were polymerized in aqueous media using me thylated (1.8)-beta -cyclodextrin (MeCD) additives. Hydrophobic monomers te rt-butyl methacrylate (tBuMA), cyclohexyl methacrylate (CMA), and 2-ethylhe xyl methacrylate (2EHMA) were each dissolved in chloroform with MeCD. Chlor oform was then evaporated to yield solid monomer/cyclodextrin complexes. Co mplexes were shown by H-1 NMR and thermogravimetric analysis (TGA) to have molar ratios of monomer to MeCD as high as 0.72/1.00. The water-soluble com plexes were readily polymerized in aqueous media using free radical initiat ion. During polymerization, hydrophobic methacrylic polymers precipitated a nd the majority of MeCD remained in solution. Poly(alkyl methacrylates) syn thesized via this method exhibited number-average molecular weights ranging from 50 000 to 150 000 with polydispersities from 3.2 to 5.5 depending on monomer structure, and isolated yields were as high as 86%. Additionally, c orresponding methacrylic/carbohydrate films were prepared and examined. Hig h molecular weight poly(tBuMA), poly(CMA), and poly(2EHMA) were blended wit h MeCD to produce optically clear films with as high as 20 wt % MeCD. Diffe rential scanning calorimetry (DSC) characterization indicated that the glas s transition temperatures of these novel carbohydrate blends were controlla ble over a 20 degreesC range depending on the relative concentration of eac h component.