Effects Of Counterions On Carboxylate PMMA And Temperature On Sulfonated PS On Ionic Aggregates Morphology Of Ionomers

In the study of ionic aggregates morphology in（random）ionomers（hereinafter referred to as ionomers）containing a small amount of pendant ion groups（≤10?15mol%）,it does not explain whether the ionic aggregates are ordered,the relationship between the origin of low temperature endothermic peak and ion transition theory of differential scanning calorimetry（DSC）and ionomer structure and performance.In this work,the neutralization reaction of methyl methacrylate?methacrylic acid copolymer（MMA?MAA）with 11.7 mol%acid groups and divalent metals（Cd,Ca and Zn）acetate was used to synthesize MMA?MAA Cd,Ca and Zn salt ionomer body,and freeze dried three ionomers in a solvent to obtain an ionomer solution;the effects of three different divalent counter ions(Cd²⁺,Ca²⁺,and Zn²⁺)on the thermal transition of the ionomer body based on MMA?MAA and the size of the three ionic aggregates are compared,and whether there is order within the ionic aggregates is explored;at the same time,the difference between the body and the ion cluster morphology in solution was compared.After 14 days of"annealing"at room temperature,the MMA?MAA ionomer produces an endothermic peak at⁶0 ^oC in the DSC thermogram,which may result from the order-disorder transition within the ion cluster;the melting enthalpy varies with the ions The effect intensity increases with the order of Cd²⁺<Ca²⁺<Zn²⁺;and the matrix glass transition temperature（T_g）and the higher temperature cluster phase T_g increase in the same order,which is due to the three ionomer cluster phases increase in crosslink density and volume fraction.Multiple Bragg peaks of ion clusters were resolved in the wide-angle X-ray scattering spectra（WAXS）of the three MMA?MAA Cd,Ca and Zn ionomers,which confirmed the ordered arrangement of the atoms within the ionic aggregates calculated by WAXS,the average diameter of ion clusters of Cd,Ca and Zn ionomers is 2.4,1.5 and 1.2 nm respectively,which is in reverse order of ionic interaction strength;in solution,only Zn salt ionomers are in WAXS.The Bragg peaks of ion clusters were resolved in Cd and Ca salt ionomers with many separate ion trimers without forming ionic aggregates,and the Zn salt ionomers through the strong interaction between Zn²⁺and?COO^-?ionic aggregates（¹.6 nm）are formed within the molecule.High-resolution transmission electron microscopy（HR-TEM）photographs of MMA?MAA Cd,Ca,and Zn ionomer bodies have detected lattice fringes between light and dark phases,which is direct evidence of order within the ion cluster,and It is observed that the ionic aggregates are spherical,and the ionic aggregates sizes of Cd and Zn salt ionomers are³.2 and 2.2 nm;the ion cluster morphology is irregular in the three ionomer solutions,but in the Cd and Zn salt ionomer solutions,there are still light and dark diffraction stripes,indicating that even a strong solvent cannot destroy the order within the ion cluster.The lyophilized polystyrene sulfonate sodium salt ionomer（SPS?Na）was vacuum heat-treated at different temperatures to obtain thermodynamic equilibrium SPS?Na at different temperatures.The effect of heat treatment at different temperatures on the T_g of SPS?Na matrix very small,it is speculated that as the heat treatment temperature increases,the ion cluster size becomes larger and the number density decreases.The two have opposite effects on Tg,so the two may cancel each other,resulting in little change in T_g;the other may be at all heat treatment temperatures,the morphological distribution of ionic aggregates reached a steady state distribution and had no effect on the change of Tg.In the WAXS spectrum of SPS?Na heat-treated at different temperatures,multiple Bragg peaks were resolved and the peak positions were basically unchanged.It also confirmed that there is order within the ion cluster,but the temperature may not affect the internal coordination structure of the ionic aggregates.