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Interpenetrating polymer networks (IPNs) based on polyurethanes.

机译:基于聚氨酯的互穿聚合物网络(IPN)。

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The morphology and properties of any simultaneous interpenetrating network (SIN) depend on the time order of three key events during its synthesis. These are: gelation of polymer I, gelation of polymer II, and phase separation of polymer I from polymer II. Metastable phase diagrams for SINs are developed. Using these diagrams, the time order of these events can be visualized and thus, controlled more effectively. Reaction mixtures for a cross-polyurethane-inter-cross-poly(methyl methacrylate) (PU-PMMA) model SIN system were followed through phase separation and gelation in terms of conversions for each polymer. Fourier transform infrared spectroscopy (FTIR), dynamic mechanical spectroscopy (DMS) and differential scanning calorimetry (DSC) were utilized. The final isothermal diagram takes the shape of a tetrahedron with its four vertices representing the two monomers (MMA and "U") and the corresponding two polymers.; Within this three-dimensional metastable phase diagram for this model SIN system, phase separation and gelations of the two polymers are indicated by various surfaces. For example, gelation of PMMA at 8% conversion gives a planar surface, and that of PU at 65% conversion gives another. The third event, phase separation, yields a curvilinear surface within the tetrahedron. These surfaces intersect with each other at lines and curves, representing unique conditions of SIN synthesis, e.g., simultaneous gelation of the two polymers, or, simultaneous phase separation and gelation of polymer I, etc. These are critical conditions in terms of the development of SIN morphology. The positions of these critical conditions can be moved within the diagram in a controlled fashion via slight changes in the system. As an example, various amounts of N,N-dimethylacrylamide monomer (DMA) were incorporated into the PMMA network by means of copolymerization.; It was also found that during the late stages of MMA polymerization, the partition coefficient of MMA monomer across the PU- and PMMA-rich phases is nearly unity. Free energy calculations (statistical thermodynamics) confirm this experimental result, and indicate that the absorption (or retainment) of MMA in either phase and its partitioning across the phases is entropy-driven and not enthalpy-driven.
机译:任何同时互穿网络(SIN)的形态和特性都取决于其合成过程中三个关键事件的时间顺序。它们是:聚合物I的胶凝,聚合物II的胶凝,以及聚合物I与聚合物II的相分离。开发了SIN的亚稳态相图。使用这些图表,这些事件的时间顺序可以被可视化,从而得到更有效的控制。按照每种聚合物的转化率,通过相分离和凝胶化来跟踪交联聚氨酯-交联-聚甲基丙烯酸甲酯(PU-PMMA)模型SIN系统的反应混合物。利用了傅里叶变换红外光谱(FTIR),动态机械光谱(DMS)和差示扫描量热法(DSC)。最终的等温图为四面体形状,其四个顶点代表两种单体(MMA和“ U”)以及相应的两种聚合物。在此模型SIN系统的三维亚稳相图中,两种聚合物的相分离和胶凝作用由各种表面指示。例如,PMMA在8%的转化率下的凝胶化产生平坦的表面,而PU在65%的转化率下的凝胶化产生另一种表面。第三事件,相分离,在四面体内产生曲线表面。这些表面在直线和曲线上相交,代表了SIN合成的独特条件,例如两种聚合物的同时凝胶化,或聚合物I的同时相分离和凝胶化等。这些是在开发SIN方面的关键条件SIN形态。这些关键条件的位置可以通过系统中的细微变化以受控方式在图中移动。例如,通过共聚将各种量的N,N-二甲基丙烯酰胺单体(DMA)掺入到PMMA网络中。还发现在MMA聚合的后期,MMA单体在富含PU和PMMA的相上的分配系数几乎是统一的。自由能计算(统计热力学)证实了这一实验结果,并表明MMA在任一相中的吸收(或保留)及其在各相之间的分配是由熵驱动的,而不是由焓驱动的。

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