Food Engineering and Packaging, Defence Food Research Laboratory, Siddarthanagar, Mysore 570011, Karnataka, India.
Int J Biol Macromol. 2011 Jan 1;48(1):50-7. doi: 10.1016/j.ijbiomac.2010.09.013. Epub 2010 Oct 23.
Nanocrystals prepared from bacterial cellulose are considered as 'green nanomaterials' depending on their renewable nature and ease of production without the involvement of hazardous chemical treatments. In this investigation, a top down approach was followed for the preparation of bacterial cellulose nanocrystals (BCNC) using a commercially available cellulase enzyme so as to retain native properties of bacterial cellulose even in its nanodimensional form. The morphological and dimensional parameters of BCNC were studied using atomic force microscope (AFM) and transmission electron microscope (TEM). Thermal properties of BCNC produced using the novel enzyme treatment and conventional sulfuric acid hydrolysis were compared. The thermal stability of enzyme processed BCNC was almost two fold higher than sulfuric acid processed ones. Further, the activation energy required for decomposition of enzyme processed BCNC was much higher than the other. Using this enzyme processed BCNC, Polyvinylalcohol (PVA) nanocomposite films were prepared and characterized. Incorporation of these nanocrystals in polymer matrix resulted in a remarkable improvement in the thermal stability as well as mechanical properties of nanocomposite films. These nanocomposites exhibited higher melting temperature (Tm) and enthalpy of melting (ΔHm) than those of pure PVA, suggesting that the addition of nanocrystals modified the thermal properties of PVA. The effective load transfer from polymer chains to the BCNC resulted in an improved tensile strength from 62.5 MPa to 128 MPa, by the addition of just 4 wt% of BCNC. Furthermore, the elastic modulus was found to increase from 2 GPa to 3.4 GPa. The BCNC obtained through cellulose treatment under controlled conditions were associated with several desirable properties and appear to be superior over the conventional methods of nanocrystals production. The enzymatic method followed in this study is expected to contribute the fabrication of high performance polymer nanocomposites in a much greener and innovative manner.
由细菌纤维素制备的纳米晶体被认为是“绿色纳米材料”，这取决于它们的可再生性和易于生产，而无需涉及危险的化学处理。在这项研究中，采用自上而下的方法，使用市售的纤维素酶制备细菌纤维素纳米晶（BCNC），以保留细菌纤维素的天然性质，即使在纳米尺寸形式下也是如此。使用原子力显微镜（AFM）和透射电子显微镜（TEM）研究了 BCNC 的形态和尺寸参数。比较了使用新型酶处理和传统硫酸水解制备的 BCNC 的热性能。酶处理的 BCNC 的热稳定性几乎比硫酸处理的 BCNC 高两倍。此外，酶处理的 BCNC 分解所需的活化能比其他的要高得多。使用这种酶处理的 BCNC，制备了聚乙烯醇（PVA）纳米复合材料薄膜，并对其进行了表征。将这些纳米晶掺入聚合物基质中，导致纳米复合材料薄膜的热稳定性和机械性能得到显著改善。这些纳米复合材料的熔融温度（Tm）和熔融焓（ΔHm）均高于纯 PVA，表明纳米晶的添加改变了 PVA 的热性能。有效载荷从聚合物链转移到 BCNC，导致添加仅 4wt％的 BCNC 时，拉伸强度从 62.5MPa 提高到 128MPa。此外，弹性模量从 2GPa 增加到 3.4GPa。在受控条件下通过纤维素处理获得的 BCNC 具有多种理想的性能，并且似乎优于传统的纳米晶生产方法。本研究中采用的酶法有望以更加环保和创新的方式制备高性能聚合物纳米复合材料。
