Infrared Characterization and Determination of Self-Association Equilibrium Constants for Methacrylic Acid Copolymers

Abstract

The synthesis of essentially random methacrylic acid (MAA) copolymers is reported. Precursor copolymers of styrene (ST) or 2,3-dimethylbutadiene (DMB) and a tert-butyldimethylsilylmethacrylate comonomer were synthesized initially by free-radical solution polymerization, followed by silyl deprotection to yield the desired amorphous MAA copolymers. The infrared characterization of these copolymers is discussed with particular emphasis placed on the effect of temperature and composition on hydrogen bonding, the formation of anhydrides at elevated temperatures, and quantitative measurements, leading to an estimation of the dimensionless equilibrium constant describing the self-association of MAA moieties. Comparisons are made to low molecular weight analogues and previous studies on ethylene-co-methacrylic acid copolymers. An important experimental finding is that the number of hydrogen-bonded carboxylic acid dimers that are formed at equilibrium is a strong function of chain stiffness.

Interactions in Miscible Blends of Poly(styrene-co-methacrylic acid) with Copolymers Containing Vinylpyrrolidone and Vinylpyridine Groups

“…Note that as we increase temperature, the “free” band in pure STMAA{9} increases in intensity at the expense of the hydrogen-bonded dimer band (top spectra moving to the right). This is simply a reflection of an equilibrium process that dictates the fraction of hydrogen-bonded MAA groups should decrease with increasing thermal motion . The “free” VPr group band, , on the other hand, just appears to broaden somewhat as the temperature is increased to 200 °C (bottom spectra moving to the right).…”

“…Since we have previously examined the infrared spectra of STMAA{9} and recently discussed the ramifications of self-association on the infrared spectra of copolymers containing VPr segments, we are in a position to summarize what we might expect to observe in the carbonyl stretching region of STMAA{9} blends with STVPr{13}. There are numerous possible interactions, and the most important are summarized in Scheme .…”

Miscibility and specific interactions in blends of poly[(styrene)-co-(cinnamic acid)] with poly(methyl methacrylate) and modified poly(methyl methacrylate)

“…Moreover, a weak band observed at 3442 cm -1 is attributed to carboxylic acid units that are intermolecularly hydrogen bonded to the π system of the phenyl groups in the PSCA copolymers. This band has already been observed by Paul [13] in the case of styrene/acrylic acid copolymers and Coleman [14] in the case of (styrene-co-methacrylic acid) copolymers. For illustrative purpose, the different hydroxyl bands of the PSCA spectrum illustrated in the same figure are obtained by performing a deconvolution procedure on the difference spectrum [(PSCA15)-(PS)] in order to eliminate the C-H bands.…”

Preparation and characterization of layered membranes constructed by sequential redox‐initiated grafting onto polyacrylonitrile ultrafiltration membranes

“…These two changes may be explained by the known effect of acid transfer from an associated to a dissociated form as the polyamine layer begins to approach and exert an influence on the acidic underlayer 27. Alternatively, the changes may be associated with different vibrational modes of the carboxylate ion:41 the transition from one mode to another occurs when conditions are favorable for the formation of an acid–base complex. A possible reaction is shown in Scheme .…”