Effect of Hydrogen Bonding on the Copolymerization of Styrene with Methacrylic Acid ALİ DURAN POLYMER TECHNOLOGY

EXPERIMENTAL PART 1. MATERIALS  Distillation of ST and MAA under reduced pressure,  Purification of Benzene and Dioxane,  Preparation of TMA according to the literature, [17]  Recrystalization of AIBN from methanol,  Chloroform was passed through activated alumina,

2. PREPARATION OF POLYMERS  The copolymerizations of ST and MAA were carried out at 60 0 C with AIBN as an initiator,  The copolymers were precipitated three times from benzene solution with methanol and dried over diphosphorus pentoxide in vacuum for several days,  Hydrolysis of Poly(ST-co-TMA) was dissolved in benzene, and methanol and conc. HCl were added, EXPERIMENTAL PART

 The solution was refluxed for 3 hours,  The solvent was removed by distillation under reduced pressure, and the residue was dissolved in a small amount of benzene and precipitated into methanol,  The completed hydrolysis of the TMA moiety was ascertained by FT-IR spectra,

3.CHARACTERIZATION OF POLYMERS  Gel permeation chromotography (GPC) was performed,  The weight average molecular weights were estimated by using the calibration curve of poly(ST) standards,  The contents of MAA in the copolymers were determined by titration in a benzene-methanol- sodium methoxide system, EXPERIMENTAL PART

4.MEASUREMENT OF FT-IR SPECTRA AND ANALYSIS  FT-IR spectra were measured with a Perkin Elmer 1720 FT-IR spectrometer,  The hydrogen bonds of carboxyls in the copolymers were analyzed from the C=O streching bands observed around 1695 and 1735 cm -1,  The molar absorption coefficients at the band maxima were estimated by lineer regression, EXPERIMENTAL PART

 The proportion (P as ) of associated carboxyls to total carboxyls was estimated from the band intensities (A 1695 and A 1735 ) and the molar absorption coefficients, EXPERIMENTAL PART

5.VISCOSITY MEASUREMENTS  The viscosities of the polymer solutions in chloroform were measured with an Ostwald viscometer at 25 0 C,  The intrinsic viscosities were estimated from the data of the solutions by the method of single point determination,

6.NMR MEASUREMENTS  1 H NMR spectra were measured at 400 MHz,  The measurements were performed on 10 wt.-% solutions in deuterated dimethylsulfoxide (DMSO-d 6 ) at C,  Tetramethylsilane was used as the reference, EXPERIMENTAL PART

RESULTS AND DISCUSSION  The P as values of the copolymers prepared in benzene are greater than those of the copolymers prepared in dioxane,  This suggests that the hydrogen bonding between MAA monomers is closely related to the formation of highly associating copolymers,

RESULTS AND DISCUSSION  The difference in the association ability between copolymers having the same composition means that the copolymers differ from one another in their microstructure.

RESULTS AND DISCUSSION  The degree of shrinkage of polymer chains by intramolecular association is closely related to the location of the associating functional groups in the polymer chain,  The degree of shrinkage is related to the position of associating MAA segments in the copolymer chain,  The degree of shrinkage of the copolymers by intramolecular association was examined by the ratio (g)

RESULTS AND DISCUSSION  The relationships between the g value and the number of associations (N as ) by intramolecular association are shown in Figure 4,  The g values decreased almost linearly with an increase in the N as value,  The near linear relationships mean that association occurs mainly between MAA segments closely located in the polymer chain.

RESULTS AND DISCUSSION  The monte-Carlo simulation of the copolymerization was performed in order to ascertain the effects of the supposed intrachain reaction on the copolymerization and the sequences of the formed copolymers.

RESULTS AND DISCUSSION  The apparent reactivity of MAA increased by the contribution of the intrachain reaction, and the features of the known solvent effects were qualitatively reproduced, although the degree of increase was rather small compared to the known solvent effects.

RESULTS AND DISCUSSION  The underestimation of the solvent effects may be due to the ‘bootstrap’ effect, which may decrease the concentration of MAA monomers in the macroradical in the distribution between macroradicals and hydrogen-bonding solvents,

RESULTS AND DISCUSSION

CONCLUSION  A close relationship between the hydrogen bond of hydrogen-bonding monomers in the copolymerization and the association properties of the prepared copolymers was found.  It was supposed that the intrachain reaction of the end radicals with MAA monomers hydrogen- bonding to MAA segments in the growing macroradicals forms copolymers with sequences and configurations favorable for intrachain association.

CONCLUSION  The copolymerizations at lower monomer concentrations in benzene gave copolymers with exceedingly higher intramolecular association ability compared to the copolymerizations in dioxane and at higher monomer concentration in benzene.