Design of Heterogeneous Nuclei Composed of Uniaxial Cellulose Nanocrystal Assemblies for Epitaxial Growth of Poly(ε-caprolactone)

• Published in: Macromolecules 2017-04, Vol.50 (8), p.3355-3364
• Main Authors: Lu, Zihao, Liu, Mingfeng, Gao, Qinwei, Yang, Danqin, Zhang, Zhisen, Xiong, Xiaopeng, Jiang, Yuan, Liu, Xiang Yang
• Format: Article
• Language: English
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/acs.macromol.6b02775

Epitaxial crystallization is the most prominent approach to achieving oriented thin films composed of semicrystalline polymers (SCPs). Nevertheless, current templates remain limited in fulfilling oriented SCPs with high-throughput coating processes. Herein, we report the first template for the epitaxial crystallization of SCPs based on a uniaxial assembly of shape-anisotropic nanocrystalscellulose nanocrystals (CNCs). The template was fabricated via a dip-coating method, leading to a uniaxial thin coating on both planar and nonplanar substrates. Such a thin coating functioned similarly to a laterally oriented SCP thin film in regulating the crystallization behaviors of poly­(ε-caprolactone) (PCL). The orientational relationship between the CNC thin coating and the PCL overlayer was studied systematically by employing multiple characterization tools including scattering, diffraction, and microscopy. Moreover, the epitaxial match based on the crystallography-regulated hydrogen-bonding networks between the two layers was confirmed by molecular modeling, in agreement with the experimental results. Besides the orientational regulation, CNCs also promoted the crystallization kinetics of PCL effectively due to the nanoepitaxial effect provided by each CNC particle. We highlight this facile assembly approach to heterogeneous nuclei for the epitaxial crystallization of SCPs and its extendability of achieving thin coatings composed of 3D-oriented SCPs on ambient substrates.