Supporting data for Regio- and stereoregular EVOH Copolymers from ROMP as Designer Barrier Materials

This work aimed to decrease the water permeability (PH2O), while simultaneously maintaining low oxygen permeability (PO2) in ethylene vinyl alcohol (EVOH) based copolymers by introducing high levels of backbone regioregularity and stereoregularity. Both regioregular atactic and isotactic EVOH samples with 75 mol% ethylene were prepared by a ring-opening metathesis polymerization (ROMP)-hydrogenation-deprotection approach and then compared to commercial EVOH(44) (containing 44 mol% ethylene) as a low PO2 standard with poor water barrier characteristics (i.e., high PH2O). The high levels of regioregularity and stereoregularity in these copolymers increased melting temperature (Tm), degree of crystallinity (χc), and glass transition temperature (Tg) compared to less regular structures. EVOH(44) demonstrated the highest Tm, but lower χc and Tg values as compared to the ROMP-derived polymers. Wide-angle X-ray scattering showed that semi-crystalline EVOH(44) exhibited a monoclinic structure characteristic of commercial materials, while ROMP-derived polymers displayed an intermediate structure between monoclinic and orthorhombic. Tensile testing showed that isotacticity resulted in brittle mechanical behavior, while the atactic and commercial EVOH(44) samples had higher tensile toughness values. Although EVOH(44) had the lowest PO2 of the samples explored, the atactic and tough ROMP-derived polymer approached this value of PO2 while having a PH2O over 3 times lower than commercial EVOH(44).

本研究旨在通过引入高比例的主链区域规整性与立体规整性，降低乙烯-乙烯醇（ethylene vinyl alcohol, EVOH）基共聚物的透水系数（PH2O），同时维持较低的透氧系数（PO2）。本研究采用开环易位聚合（ring-opening metathesis polymerization, ROMP）-加氢-脱保护法，制备了乙烯摩尔分数为75%的区域规整无规立构与等规立构EVOH样品，并以商用EVOH(44)（乙烯摩尔分数为44%）作为低透氧参比标准——该商用样品虽透氧系数较低，但水阻隔性能较差（即透水系数偏高）。相较于规整度更低的聚合物结构，这类共聚物中高比例的区域规整性与立体规整性可提升其熔融温度（Tm）、结晶度（χc）与玻璃化转变温度（Tg）。EVOH(44)的熔融温度最高，但其结晶度与玻璃化转变温度均低于ROMP法制备的聚合物。广角X射线散射结果显示，半结晶的EVOH(44)呈现商用EVOH典型的单斜晶系结构，而ROMP法制备的聚合物则呈现介于单斜晶系与正交晶系之间的中间态结构。拉伸测试表明，等规立构结构会使材料呈现脆性力学行为，而无规立构样品与商用EVOH(44)则具备更高的拉伸韧性。尽管在所测试的所有样品中，EVOH(44)的透氧系数最低，但无规立构且高韧性的ROMP法制备聚合物的透氧系数已接近该值，同时其透水系数较商用EVOH(44)低3倍以上。