Benicewicz BC, Smith ME, Earls JD, Priester RD, Setz SM, Duran RS, Douglas EP
Departments of Chemistry and Materials Science and Engineering, University of Florida, Gainesville, Florida 32611.
Macromolecules. 1998 Jul 28;31(15):4730-8. doi: 10.1021/ma980058m.
The effect of magnetic fields on the orientation and properties of 4,4'-bis(2,3-epoxypropoxy)-alpha-methylstilbene cured with sulfanilamide has been studied. This epoxy system is initially isotropic and forms a smectic A phase upon curing. A magnetic field was applied during the cure reaction, resulting in alignment of the molecules along the direction of the applied field. Measurement of the orientation parameter of the fully cured material by wide-angle X-ray scattering (WAXS) showed that orientation improved with an increase in field strength. The orientation parameters of the smectic layer normals calculated from the inner reflection of the WAXS pattern attained a maximum level of approximately 0.8 at a field strength of approximately 12 T. The orientation parameters calculated from the outer reflection of the WAXS pattern were considerably lower, possibly due to the presence of amorphous regions associated with domain boundaries or the loss of molecular alignment within the smectic layers due to topological restrictions of the cross-linking sites. Orientation resulted in an anisotropic linear thermal expansion coefficient after curing, although the overall volumetric expansion was constant. The elastic tensile modulus increased with the square of the orientation parameter, attaining a maximum value of 8.1 GPa, compared to 3.1 GPa for the unoriented material. The change in modulus with orientation could be fit with a simple model for the modulus of anisotropic materials.
研究了磁场对用磺胺固化的4,4'-双(2,3-环氧丙氧基)-α-甲基芪的取向和性能的影响。该环氧体系最初是各向同性的，固化后形成近晶A相。在固化反应过程中施加磁场，导致分子沿外加磁场方向排列。通过广角X射线散射（WAXS）测量完全固化材料的取向参数表明，取向随场强增加而改善。从WAXS图案的内反射计算得到的近晶层法线的取向参数在约12 T的场强下达到约0.8的最大值。从WAXS图案的外反射计算得到的取向参数则低得多，这可能是由于与畴界相关的非晶区域的存在，或者是由于交联位点的拓扑限制导致近晶层内分子排列的丧失。固化后，取向导致各向异性的线性热膨胀系数，尽管总体积膨胀是恒定的。弹性拉伸模量随取向参数的平方增加，达到最大值8.1 GPa，而未取向材料为3.1 GPa。模量随取向的变化可以用各向异性材料模量的简单模型来拟合。
