High-performance polyurethane nanocomposites based on UPy-modified cellulose nanocrystals

Tian, DL (Tian, Donglin)^[ 1,2 ] ; Wang, FF (Wang, Fenfen)^[ 1,2 ] ; Yang, ZJ (Yang, Zhijun)^[ 1,2 ] ; Niu, XL (Niu, Xiling)^[ 1,2 ] ; Wu, Q (Wu, Qiang)^[ 1,2 ] ; Sun, PC(Sun, Pingchuan)^[ 1,2,3 ]

CARBOHYDRATE POLYMERS, 219: 191-200

DOI: 10.1016/j.carbpol.2019.05.029

Abstract

Densely H-bonding assemblies are the key strategy found by nature to enhance the rupture strength of natural polymers without sacrificing their toughness, such as spider silk, while it still remains a great challenge using such intriguing strategy to prepare high-performance synthesized polymer or biopolymer enhanced polymer nanocomposites. To address this challenge, we report here a bio-inspired strategy using densely H-bonding assembly for facile fabrication of high performance polyurethane (PU) nanocomposites reinforced by hydroxylrich cellulose nanocrystals (CNCs) functionalized with 2-ureido-4-[1 H]-pyrimidinone motifs (CNC-UPy) containing self-complementary hydrogen bonds. These PU/CNC-UPy nanocomposites showed remarkably improved mechanical strength without sacrificing the elongation at break and toughness compared to pure PU matrix. Differential scanning calorimetry(DSC) results indicated that CNC-UPy could induce the formation of long range ordering of hard segment domains, due to the strong hydrogen bonding interactions between UPy motifs attached on CNC-UPy and PU matrix. Furthermore, wide angle X-ray diffraction (WAXD) measurements demonstrated that the strain-induced crystallization (SIC) was enhanced significantly by introducing CNC-UPy into PU, leading to a large stress at break. The enhanced interfacial H-bonding interactions between CNC and PU though UPy anchoring could overcome the inherent trade-off between the stiffness and toughness of polymer composites. The proposed bio-inspired strategy using densely H-bonding assembly will be with more extensive application prospects.