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Reinforced Mechanical Properties and Tunable Biodegradability in Nanoporous Cellulose Gels - Poly(L-lactide-co-caprolactone) Nanocomposites Kai Li, Junchao Huang, Huichang Gao, Yi Zhong, Xiaodong Cao, Yun Chen, Lina Zhang, and Jie Cai Biomacromolecules, Just Accepted Manuscript • DOI: 10.1021/acs.biomac.6b00109 • Publication Date (Web): 09 Mar 2016 Downloaded from http://pubs.acs.org on March 12, 2016
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Biomacromolecules
Reinforced Mechanical Properties and Tunable Biodegradability in Nanoporous Cellulose Gels - Poly(L-lactide-co-caprolactone) Nanocomposites
Kai Lia, Junchao Huanga, Huichang Gaob, Yi Zhonga, Xiaodong Caob, Yun Chenc, Lina Zhanga, Jie Cai*a a
College of Chemistry & Molecular Sciences, Wuhan University, Wuhan, 430072, People’s Republic of China b
School of Materials Science and Engineering, South China University of Technology, Guangzhou, 510641, People’s Republic of China
c
Department of Biomedical Engineering, School of Basic Medical Science, Wuhan University, Wuhan, 430071, People’s Republic of China
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Biomacromolecules
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Abstract Incorporation of nanofillers into aliphatic polyesters is a convenient approach to create new nanomaterials with significantly reinforced mechanical properties compared to the neat polymers or conventional composites. Nanoporous cellulose gels (NCG) prepared from aqueous alkali hydroxide/urea solutions can act as alternative reinforcement nanomaterials for polymers with improved mechanical properties. We report a simple and versatile process for the fabrication of NCG/poly(L-lactide-co-caprolactone) (NCG/P(LLA-co-CL) nanocomposites through in situ ring-opening polymerization of L-lactide (LLA) and ε-caprolactone (ε-CL) monomers in the NCG. The volume fraction of the NCG in the nanocomposites was tunable and ranged from 4.5% to 37%. Fourier transform infrared (FT-IR), X-ray diffraction (XRD) and differential scanning calorimetry (DSC) results indicated that P(LLA-co-CL) were synthesized within the NCG and partially grafted onto the surface of the cellulose nanofibrils. The glass-transition temperature (Tg) of the NCG/P(LLA-co-CL) nanocomposites could be altered by varying the molar ratio of LLA:ε-CL and was affected by the volume fraction of NCG. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) images confirmed that the interconnected nanofibrillar cellulose network structure of the NCG was finely distributed and preserved in the P(LLA-co-CL) matrix after polymerization. The dynamic mechanical analysis (DMA) results showed remarkable reinforcement of the tensile storage modulus (E´) of the P(LLA-co-CL) nanocomposites in the presence of NCG, especially above the Tg of the P(LLA-co-CL). The modified percolation model
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Biomacromolecules
agreed
well
with
the
mechanical
properties
of
the
NCG/P(LLA-co-CL)
nanocomposites. The introduction of NCG into the P(LLA-co-CL) matrix improved the mechanical properties and thermal stability of the NCG/P(LLA-co-CL) nanocomposites. Moreover, the NCG/P(LLA-co-CL) nanocomposites have tunable biodegradability and biocompatibility and potential applications in tissue engineering repair, biomedical implants, and packing.
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Introduction Biocompatible and biodegradable aliphatic polyesters have been increasingly used in many fields, including medicine, pharmacy, and packing, in recent years. Among these polyesters, poly(L-lactic acid) (PLA), polycaprolactone (PCL) and their copolymers
have
received
significant
attention
for
numerous
biomedical
applications.1-5 P(LLA-co-CL) shows excellent biocompatibility, rapid degradability in vivo, good miscibility with other polymers and better drug permeability than PLLA and PCL.4, 6-8 The exploitation of P(LLA-co-CL) is, however, hampered by its poor mechanical properties, which are mainly attributable to the different reactivity ratios of ε-caprolactone (ε-CL) and L-lactic acid (LLA) monomers (γCL < 1
