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Four inorganic chlorides were introduced into hydrochloric acid hydrolysis to extract cellulose nanocrystals (CNCs) from microcrystalline celluloses (MCC) under hydrothermal conditions. The as-prepared CNCs were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT–IR), and thermogravimetric analysis (TGA). The role of inorganic chlorides including ferric chloride hexahydrate (FeCl3·6H2O), copper chloride dihydrate (CuCl2·2H2O), aluminum chloride (AlCl3), and manganese chloride tetrahydrate (MnCl2·4H2O) in the extraction and properties of high quality CNCs was determined. It is observed that the introduction of inorganic chlorides obviously enhanced the hydrolysis process through faster degradation of the disordered region of cellulose. Compared with those for pure hydrochloric acid hydrolysis, smaller diameter and a larger length to diameter ratio of CNCs could be obtained through salt-catalyzed hydrolysis, which could contribute to greater enhancement on the mechanical properties of polylactic acid (PLA) nanocomposite films. Moreover, it is found that the highest reinforcing effects for the PLA matrix as well as the best transparency among all the nanocomposites were achieved in the presence of ferric chlorides, benifiting from the largest length to diameter ratio and most white of the corresponding CNCs. These results show that the use of salt-catalyzed hydrolysis especially ferric chloride has a significant improvement in achieving the energy-efficient and cost-effective conversion of cellulose starting materials into high quality CNCs.

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Electrospun nanofibrous membranes of poly­(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) seems not to be ideal for biomedical applications because of their hydrophobicity, and high crystallinity, as well as weak mechanical properties. It is found that hydrophilic drug such as tetracycline hydrochloride (TH) generally is located on the hydrophobic surface of electrospun PHBV nanofibrous membranes, leading to fast drug release. Therefore, we used cellulose nanocrystals (CNCs) as rigid organic nanofillers for PHBV nanofibrous membranes to enhance their mechanical, thermal, and hydrophilic properties. The influences of the CNC contents on microstructures and properties of composite nanofibrous membranes were studied. It is found that at 6 wt % CNC content, the increase of tensile strength by 125%, Young’s modulus by 110%, and maximum decomposition temperature (T max) by 24.3 °C could be achieved, which could be contributed to strong hydrogen bonding between PHBV and CNCs. Moreover, with the introducing of the hydrophilic CNCs, the hydrophilicity of composite nanofibrous membranes was improved gradually. More importantly, good cytocompatibility, high drug loading and long-term sustained release property of composite nanofibrous membranes could be achieved. The maximum drug loading and drug loading efficiency were 25 and 98.8%, respectively, and more than 86% drug content was delivered within 540 h for the nanofibrous composite membranes with 6 wt % CNC content.

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