Computational Study of the Formation Reaction of Polyacid Precursors of Glass-Ionomer Materials

The formation of polyacids in a glass-ionomer cement was computationally modeled. The polyacid modelled is an oligomer made up of three molecules: acrylic acid, itaconic acid and an additional molecule that acts as a spacer group between the previous two. Acryloyl and meta-acryloyl derivatives of some amino acids and related molecules such as N-vinyl pyrrolidone and N-vinyl caprolactam were used as spacer groups. Some of these molecules have been previously used experimentally as spacer groups. In this work the spacer behaviour of 15 different molecules was investigated. To our knowledge, this is the first computational attempt to model some promising molecules to be incorporated into glass-ionomer dental cements. The results revealed the best structural arrangement for the investigated molecules.

Synthesis of Lignin-Based Polyacid in an Acidic Ionic Liquid: A Green Method to Improve the Performance of Lignin as Catalyst in Urea-Formaldehyde Resin

The aim of this research was to investigate the effect of ionic liquid treated lignin-based polyacid as a catalyst for urea-formaldehyde(UF)resins.Esterification of lignin was carried out,without any catalyst,with anhydride maleic and 1-butyl-3-methylimidazolium hydrogen sulfate[Bmim][HSO 4]as acidic ionic liquid to form maleated lignin-based polyacids(MA-IL).The performance of MA-IL as UF resin catalyst was respectively compared to hyroxymethylated lignin-based polyacid(MA-HL)and to NH 4 Cl.The FTIR analysis indicated that the propor-tion of-COOH and C-O bonds increased due to the esterification of lignin with ionic liquid rather than its hyr-oxymethylation.Physicochemical tests indicated that the gelation time of the UF resin was shorter by adding MA-IL when compared to NH 4 Cl and MA-HL,respectively.DSC analysis showed that the addition of MA-IL significantly decreased the temperature peak(Tp)of the UF resin;as the Tp of the UF resin with 2 wt%MA-IL was lower than with MA-HL and NH 4 Cl,respectively.The panel test results of plywood bonded with a UF resin with a MA-IL level increasing from 1%to 3%,effectively improved the mechanical strength,water resistance and formaldehyde emission even higher than with MA-HL and NH 4 Cl,respectively.

Visualization of Two-dimensional Single Chains of Hybrid Polyelectrolytes on Solid Surface

The polyacidic character of polyoxometalate(POM)clusters endows high ionic conductivity,making these clusters good candidates for solar and fuel cells.Covalent bonding of clusters to polymer chains creates poly(POM)s that are polyelectrolytes with both cluster functions and polymer performance.Thus,solution-processable poly(POM)s are expected to be used as key materials in advanced devices.Further understanding of poly(POM)s will optimize the preparation process and improve device performance.Herein,we report a study of the first linear poly(POM)s by directly visualizing the chains using scanning transmission electron microscopy.Compared with traditional polymers,individual clusters of poly(POM)s can be directly visualized because of the resistance to electron-beam damage and the high contrast of the tungsten POM pendants.Thus,cluster aggregates with diverse shapes were observed.Counting the number of clusters in the aggregates allowed the degree of polymerization and molecular weight distribution to be determined,and studying the aggregate shapes revealed the presence of a curved semirigid chain in solution.Further study of shape diversity revealed that strong interactions between clusters determine the diverse chain shapes formed during solution processing.Fundamental insight is critical to understanding the formation of poly(POM)films from solutions as key functional materials,especially for fuel and solar cells.