In order to determine if the alternating tendency of styrene with fluorinated styrenes in free radical copolymerizations correlates with the strength and/or extent of π-π stacking interactions between aromatic fluorocarbons and aromatic hydrocarbons, styrene (St) was copolymerized with 2,3,4,5,6-pentafluorostyrene (PFS) and 4-fluorostyrene (4FS) under a variety of conditions. For the copolymerization of styrene with PFS at 25 °C, r St r FS ) 0.048 and 0.069 in bulk and toluene, respectively, using tert-butylperoxy pivalate as the initiator. For the copolymerization of styrene with PFS at 70 °C using benzoyl peroxide as the initiator, r St r FS ) 0.17 in bulk and r St r FS ) 0.14 in toluene. For the copolymerization of styrene with 4FS, r St r FS ) 0.69 at 25 °C under redox conditions and r St r FS ) 0.62 at 70 °C in bulk. As confirmed by 1 H, 13 C, and 19 F one-dimensional NMR and 1 H-13 C heteronuclear single quantum coherence and 1 H-1 H nuclear Overhauser effect two-dimensional NMR spectroscopy results, St and 4FS tend to form random copolymers whereas the St-PFS copolymers tend to alternate with the alternating tendency increasing with decreasing temperature. The glass-transition temperatures determined by differential scanning calorimetry of the St-PFS copolymers are elevated relative to their mole-average values, whereas those of the corresponding homopolymer blends and the St-4FS copolymers occur at mole-average values. The water and ethylene glycol contact angles of both the St-PFS and St-4FS copolymer films occur at their mole-average values.
The synthesis, characterization, and ring-opening polymerization of a new cyclic carbonate monomer containing an allyl ester moiety, 5-methyl-5-allyloxycarbonyl-1,3-dioxan-2-one (MAC), was performed for the first time. MAC was synthesized in five steps in good yield beginning from the starting material, 2,2-bis(hydroxymethyl)propionic acid. Subsequent polymerization and copolymerizations of the new cyclic carbonate with rac-lactide (rac-LA) and ⑀-caprolactone (CL) were attempted. Rac-LA copolymerized well with MAC, but CL copolymerizations produced insoluble products. Oligomeric macroinitiators of MAC and rac-LA were synthesized from stannous ethoxide, and both macroinitiators were used for the controlled ring-opening polymerization of rac-LA. The polymerization kinetics were examined by monitoring the disappearance of the characteristic COO ring stretch of the monomer at 1240 cm Ϫ1 with real-time in situ Fourier transform infrared spectroscopy. Postpolymerization oxidation reactions were conducted to epoxidize the unsaturated bonds of the MAC-functionalized polymers. Epoxide-containing polymers may allow further organic transformations with various nucleophiles, such as amines, alcohols, and carboxylic acids. NMR was used for microstructure identification of the polymers, and size exclusion chromatography and differential scanning calorimetry were used to characterize the new functionalized poly(ester-carbonates).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.