A deeper exploration of the relation between sulfonation degree and retanning performance of aromatic syntans

It is well‑known that the sulfonation degree(DS)of aromatic syntan is an important factor affecting its retanning performances.But the quantitative relation between DS and syntan property and the influencing mechanism of DS on syntan property are not clarified.In this work,five phenolic formaldehyde syntans(PFSs)with the same polym‑erization degree but varying DS were prepared to investigate the effect of DS on the properties of syntan and crust leather.It was found that the absolute value of zeta potential and the particle size of PFS decreased with increasing DS in aqueous solution.Molecular dynamic simulation results proved that the DS of PFS was a major contributor to electrostatic interaction and hydrogen bonding in the PFS–water system and greatly affected the aggregation and dispersion of PFS in aqueous solution.The PFS with a low DS was prone to aggregate to large particles in aqueous solution because of low intermolecular electrostatic repulsion and less hydrogen bonds and therefore can be used to increase the thickness and tightness of leather.The PFS with a high DS presented a small particle size with more anionic groups in aqueous solution,thereby sharply decreasing the positive charge of leather surface and facilitat‑ing the penetration of the post‑tanning agents into the leather.These results might be scientifically valid for rational molecular design of syntans and more productive use of syntans in leather making.

Effect of Sulfonation Degree on Performance of Proton Exchange Membranes for Direct Methanol Fuel Cells

A series of proton exchange membranes based on sulfonated polyarylene ether ketones（SPAEKs） was used to study the effect of sulfonation degree on proton conductivity, methanol permeation and performance of direct methanol fuel cells（DMFCs）. Dependences of physical characteristics of the membranes, i. e., proton conductivity, water uptake, swelling ratio, methanol permeability and ion exchange capacity（IEC） were systematically studied. Both methanol permeability and proton conductivity of the SPAEK membrane grow rapidly as the increase in sulfonation degree since methanol molecules and protons share the same transfer channel. However, the methanol permeability plays more important role comparing to proton conductivity. As a result, the SPAEK membrane with a medium sulfonation degree（60%） was found to yield the best performance in a DMFC due to the acquirement of balanced conductivity and methanol permeability.

Novel,tadpole-shaped,polyhedral oligomeric silsesquioxane containing sulfonated block copolymer for humidity sensing

Due to the"trade-off"effect between the high water adsorption and low stability under high Relative Humidity of polymer matrix,fabrication of resistive-type polymer-based humidity sensors with a wide impedance response and excellent stability in high relative humidity remains a great challenge.Aim at solving that,a novel polymeric humidity sensing matrix,specifically a tadpole-shaped,polyhedral oligomeric silsesquioxane(POSS)containing block copolymers(BCPs)of POSS-poly(methyl methacrylate)-poly styrene(POSS-PMMA-SPS)were proposed.This novel BCP was synthesized using atom transfer radical polymerization(ATRP)employing a two-step approach,and following post sulfonation,a series of sulfonated BCPs(POSS-PMMA-SPS)with different sulfonation degree was obtained.The subject humidity sensors were produced using different sulfonated BCPs employing a dip-coating technique,and three wide-impedance response humidity sensors were produced.Each of these sensors exhibited an excellent humidity-sensing response of mo re than 104 within the humidity range from 11%to 95%RH.In particular,the humidity sensor S-6 that had a proper degree of sulfonation presented a relatively fast response(t90%of 11 s and 80 s in both the water adsorption and desorption processes),and superior repeatability for more than 30 days.