¹³C MAS NMR Study of Poly(methacrylic acid)–Polyether Complexes and Multilayers

Abstract

Hydrogen-bonded interpolymer complexes are widely used as stimuli-responsive materials. This solid-state 13 C MAS NMR spectroscopy study examines the influence of water and temperature on the hydrogen bond structures of 13 C-labeled poly(methacrylic acid) (PMAA) complexes with poly(ethylene oxide) (PEO) and poly(vinyl methyl ether) (PVME). The spatial variation of the inter-and intrapolymer hydrogen bonds in the dried bulk complexes and supported multilayers was measured by 2D 13 C exchange (EXSY) NMR. In contrast to earlier studies of PAA complexes, the cross-peak intensities of the PMAA complexes are primarily due to 13 C spin exchange rather than H-bond exchange due to the use of 13 Clabeled PMAA and slower dynamics. The 13 C− 13 C spin diffusion between the carbonyl groups with intra-versus interpolymer hydrogen bonds indicates interatomic distances of <7 Å, consistent with interpolymer and the different intra-PMAA hydrogen bonds occurring together along the PMAA chain segments or in nanodomains in close proximity rather than isolated clusters. The fractional population involved in the spin diffusion corresponded to the population of the stronger cyclic dimer, such that PMAA−PEO complex > PVME complex > PEO supported multilayers > PVME supported multilayers. For the multilayer films, there are fewer of the stronger, more ordered cyclic dimer hydrogen bonds due to the disordering effect of the interfaces.

Protein adsorption through Chitosan–Alginate membranes for potential applications

“…The average diameter of MHH particle was determined [ 70 ]. Then, the values of D p and D f were calculated under the given conditions explained below.…”

“…Then, the values of D p and D f were calculated under the given conditions explained below. R p (m) is the average radius of the adsorbent particles, ε is the film thickness (10 −5 m) [ 70 ] and C s and C L are the concentration of adsorbate in solid and liquid phase, respectively. Debnath et al [ 70 ] assumed that the intraparticle diffusion will be the rate-limiting step if the calculated intraparticle diffusion coefficient ( D p ) value is in the range 10 −15 –10 −18 m 2 s −1 .…”

“…R p (m) is the average radius of the adsorbent particles, ε is the film thickness (10 −5 m) [ 70 ] and C s and C L are the concentration of adsorbate in solid and liquid phase, respectively. Debnath et al [ 70 ] assumed that the intraparticle diffusion will be the rate-limiting step if the calculated intraparticle diffusion coefficient ( D p ) value is in the range 10 −15 –10 −18 m 2 s −1 . For the calculated film diffusion coefficient ( D f ) value ranging from 10 −10 to 10 −12 m 2 s −1 the rate-limiting step is controlled by film diffusion.…”

Mechanism of Enhanced Nifedipine Dissolution by Polymer-Blended Solid Dispersion through Molecular-Level Characterization

“…The 13 C peaks of HPMC and EUD-S were assigned based on previous reports. 18,33 The change in the chemical shift of 13 C peaks of HPMC was small among polymer SPDs, while the peak shapes of C β , C γ , C δ , and C ε of HPMC were slightly changed by EUD-S blending; the peak width of HPMC at approximately 70−90 ppm was sharper for HPMC/EUD-S SPD than for HPMC SPD. This result is in agreement with a previous report that indicated that the hydrogen bonds among the hydroxyl groups of HPMC were disrupted by the molecular interaction between HPMC and EUD-S, leading to a change in the peak shape of HPMC.…”

“…The carbonyl group of the methyl methacrylate of EUD-S is likely involved in the nondimer structure. 33 In our previous study, the relative carbonyl peak areas of the cyclic-and open-dimer structures at 186.3 and 180.4 ppm in EUD-S were reduced in comparison with that of the nondimer structure at 177.7 ppm by HPMC blending with EUD-S. 18 The polymer blending of HPMC with EUD-S led to the formation of hydrogen bonds between HPMC and EUD-S, which resulted in the cleavage of the dimeric structure of methacrylic acid in EUD-S. In the present study, it was demonstrated that the dimer structure in EUD-S was cleaved depending on the amount of HPMC in HPMC/EUD-S SPD.…”