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The research team of Professor Huang Jin and Associate Professor Gan Lin from Southwest University proposed a percolation / crosslinking dual network collaborative strategy to optimize the mechanical properties of crystallizable polymer materials
2020-01-09 Source: Polymer Technology

Cross-linking and percolation methods are widely used in the modification of highly elastic crystallizable materials, but each has certain limitations when applied to modified crystalline polymer materials, such as the difficulty in controlling the degree of cross-linking, which easily leads to material strength and The toughness is difficult to balance, and the heterogeneous nucleation of the percolation filler can easily increase the crystallinity of the material matrix. Therefore, how to maintain the simultaneous increase of the strength and toughness of the crystallizable elastic material is an interesting issue.

Eucommia gum (EUG) is a class of elastic materials with crystallization ability, especially the highly symmetrical trans-isoprene structure, which is easy to crystallize at room temperature, has limited its application. In response to the above problems, the research team of Professor Huang Jin and Associate Professor Gan Lin used biomass-derived cellulose nanocrystals (CNC), a rigid rod-shaped nano-filler, to propose a percolation / crosslinking dual network synergy strategy, and introduced chemical modification in EUG The prepared sulfhydrylized CNC (mCNC) utilizes a highly efficient thiol-vinyl Click-type reaction to couple the mCNC filler and the EUG matrix through covalent bonds, thereby realizing the optimization of the mechanical properties of the nanocomposite system (see Figure 1).

Figure 1. Schematic diagram of the EUG / mCNC nanocomposite preparation process and cross-linking / permeation dual network structure.

In the nanocomposite system, mCNC forms a percolation network in the EUG matrix, which is confirmed by dynamic mechanical analysis (see Figure 2). Furthermore, combining the cross-linked network formed by the filler and the matrix, the mechanism of mechanical enhancement of the synergistic effect of the dual network and its influence on the crystallinity of the EUG matrix were systematically discussed. The thiol-vinyl Click type reaction between the mCNC filler and the EUG matrix increases the interfacial compatibility between the filler and the matrix and reduces the possibility of matrix crystallinity in the nanocomposite. The formation of ZnO shows a significant enhancement effect. The inhibition of matrix crystallization and the percolation enhancement effect of the filler synergistically achieve the simultaneous strengthening and toughening of the EUG / mCNC nanocomposite, which enriches the structural design and performance control ideas of crystalline polymer elastic materials.

Figure 2. Curves of storage modulus (A) and loss factor (B) of EUG / mCNC nanocomposites with increasing temperature, and the dependence of measured storage modulus and mCNC content on theoretical curves of percolation network models Anastomosis (C).

The research results were recently published in ACS Applied Bio Materials (doi: 10.1021 / acsabm.9b00901). The first author of the thesis is Wang Yuhuan , a postgraduate student in the School of Chemistry and Chemical Engineering of Southwest University.

Paper link: http://pubs.acs.org/doi/abs/10.1021/acsabm.9b00901

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