Grafting onto Starch. IV. Graft Copolymerization of Methyl Methacrylate by Use of AIBN as Radical Initiator

Grafting of poly(methyl methacrylate) onto starch has been investigated in aqueous medium by using AIBN as radical initiator. Starch-g-PMMA has been characterized by determination of starch in the graft copolymer. Percentage of grafting has been determined as functions of concentration of monomer, concentration of initiator, reaction time, and temperature. From scanning electron microscopic studies, evidence for grafting of PMMA onto starch has been presented.     

Synthesis and properties of poly(aryl ether benzimidazole) copolymers for high-temperature fuel cell membranes

A series of poly(aryl ether benzimidazole) copolymers bearing different aryl ether linkage contents were synthesized by condensation polymerization in polyphosphoric acid (PPA) by varying the feed ratio of 4,4′-dicarboxydiphenyl ether (DCPE) to terephthalic acid (TA). As the ether unit content in the copolymer increased, the solubility of the copolymer in PPA and N,N′-dimethylacetamide/LiCl improved. For example 3–7 wt.% DMAc solution containing 2 wt.% of LiCl could be prepared from the copolymers. XRD studies revealed that the incorporation of flexible aryl ether linkages increased the chain d-spacings of the polymer backbones and decreased the crystallinity of the copolymers. Still, these copolymers having ether linkages showed reasonably good thermal/mechanical stability and high proton conductivity. For example, the copolymer with 30 mol% ether linkage had a tensile strength of 43 MPa (at 26 °C and 40% relative humidity) at an acid doping level of 7.5 mol H₃PO₄ and a proton conductivity of 0.098 S cm⁻¹ (at 180 °C and 0% relative humidity) at an acid doping level of 6.6 mol H₃PO₄.     

POLY(ETHER-BLOCK-SULFONATED ESTER)COPOLYMERS. I. PHASE STRUCTURE AND PHYSICAL PROPERTIES*

The physical properties and a microphase-separated structure of multiblockcopolymers based on flexible segments of poly(1,4-oxytetramethylene)(PTMO) and rigid crystalline segments of poly(butylene terephthalate) (PBT) modified by ionic units were studied. Ionic copolymers were characterizedby limiting viscosity number, melt flow index, and tensile property measurements. The mechanical behavior of ionic poly(ether-block-sulfonated ester)(PESE) copolymers can be compared to that of conventional hard-soft thermoplasticelastomers. The phase structure was studied using differential scanningcalorimetry (DSC). Clearly, the DSC results show that the ionic unitsin the polyester segments have no significant influence on the microphaseseparation structure of PESE. A small reduction of the degree of crystallinitywith increasing content of ionic groups in the polyester rigid segments wasobserved. This results from the effect of ionic forces caused by incorporationof ionic units in the polyester segments.

     

Sulfonated poly(arylene ether sulfone) ionomers containing fluorenyl groups for fuel cell applications

A series of sulfonated poly(arylene ether sulfone)s (SPEs) containing fluorenyl groups as bulky components were synthesized and characterized for fuel cell applications. Introduction of disodium 3,3′-disulfo-4,4′-difluorophenyl sulfone (SFPS) monomer gave ionomers with high acidity and accordingly high proton conductivity as well as high proton diffusion coefficient (D_σ) at low humidity. The membrane of SPE60 (where the number denotes mole percentage of the component containing sulfonic acid groups; IEC (ion exchange capacity) = 1.68 mequiv./g) exhibited high proton conductivity of 4.6 × 10⁻³ S/cm at 40% RH and 80 °C, which is one order of magnitude higher than that (6 × 10⁻⁴ S/cm) of our previous SPE (SPE-1, IEC = 1.58 mequiv./g). D_σ of SPE60 membrane was ca. 4 times higher than that of the SPE-1 membrane at low water volume fraction. SPE membranes showed good oxidative and hydrolytic stability as well as favorable thermal and mechanical properties. Small-angle X-ray scattering analyses showed that the phase separation of SPE membranes was much less developed than that of the perfluorinated Nafion membrane which accounts for lower hydrogen and oxygen permeability of the former membranes.     

Specific interactions and miscibility of blends of poly(ε-caprolactam) and sulfonated PEEK ionomer

Sulfonation of poly(oxy-1,4-phenyleneoxy-1,4-phenylenecarbonyl-1,4-phenylene), PEEK, improves its miscibility with poly(ϵ-caprolactam), Nylon-6 (N6). This article describes the thermal transitions and the specific interactions that occur for blends of the free acid derivative (H-SPEEK) and the lithium (Li-SPEEK) and zinc salts (Zn-SPEEK) of sulfonated PEEK (19.2 mol % sulfonation) with N6. The interactions responsible for miscibility were characterized by Fourier transform infrared (FTIR) spectroscopy. For blends of H-SPEEK and N6, miscibility is due to hydrogen bonding between the sulfonic acid and the amide group. For blends of N6 with the salts of SPEEK the specific interaction involves an ion-dipole complex of Li⁺ with the amide carbonyl or Zn²⁺ with the amide nitrogen. The relative strengths of the intermolecular interactions for the three types of blends increased as the cation was varied in the order: H⁺ < Li⁺ < Zn²⁺, and the T_gs of the mixtures increased in the same order. © 1996 John Wiley & Sons, Inc.     

Dynamics of novel polybutadiene ionomers

The dynamics of novel ionomers based on a low‐molecular‐weight polybutadiene with zinc acrylate moieties were investigated as a function of the number of ionic bonds by using a combination of calorimetry, dielectric broadband spectroscopy and rheology. We find that the ionic bonds have profound effects on the mechanical properties, including the introduction of a sol–gel transition. However, all techniques consistently indicate that the segmental dynamics of the polymer chains remain largely unaffected, and only very small changes in the glass transition were observed. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1074–1079     

Phase transition behavior of a poly(oxyethylene-b-butylene adipate) ionomer with shape memory properties

A series of biodegradable poly(oxyethylene-b-butylene adipate) ionomers (POBAi) were prepared by two-step in situ polymerization using adipic acid, 1,4-butanediol and mixed monomers of bis(poly(oxyethylene)) sulfonated dimethyl fumarate. The chemical composition of these POBAi was ascertained by ¹H NMR spectroscopy. The objective of this study was to investigate the shape memory effect of POBAi containing ionomer compared to non ionic POBA. It was observed that POBA5.0i showed a good shape memory effect than that of POBA 2.5 mol% or none of ionic group due to much physical cross-linking point by rich ionic group. Stress-induced phase transition was investigated during the shape deformation and recovery process using a wide-angle X-ray diffractometer (WAXD). The POBA crystal phase transition from β- to α-form was observed in all POBA samples by either thermal treatment or physical drawing. The α-form crystal did not recover to the initial β-form during the recovery process because the monoclinic α-form crystal is structurally more stable than the orthorhombic β-form crystal.     

含不同金属离子的EPDM磺酸盐离聚物的研究

合成了含不同金属离子Na~+、Mg~(2+)、Zn~(2+)和Al~(3+)的四种乙丙三元共聚物(EPDM)磺酸盐离聚物, 红外光谱和氧瓶燃烧法测定了磺酸基的存在和含量。动态力学结果表明, 离聚物中碳酸盐基团可能以多重离子对形式聚集; 热重法指出, EPDM磺酸盐的热稳定性为钠盐>锌盐>镁盐>铝盐。考察了它们在二甲苯-正己醇混合溶剂中, 比浓粘度随浓度、温度变化的规律, 初步分析了各种金属盐的差异及其原因。