Morgado Daniella L, Rodrigues Bruno V M, Almeida Erika V R, Seoud Omar A El, Frollini Elisabete
Macromolecular Materials and Lignocellulosic Fibers Group, Center for Research on Science and Technology of BioResources, Institute of Chemistry of São Carlos, University of São Paulo, P.O. Box 780, São Carlos 13560-970, Brazil.
Institute of Chemistry, University of São Paulo, P.O. Box 26077, São Paulo 05513-970, Brazil.
Materials (Basel). 2013 Jun 14;6(6):2410-2435. doi: 10.3390/ma6062410.
This paper describes the results obtained on the preparation of films composed of linter cellulose and the corresponding acetates. The acetylation was carried out in the LiCl/DMAc solvent system. Films were prepared from a LiCl/DMAc solution of cellulose acetates (degree of substitution, DS 0.8-2.9) mixed with linter cellulose (5, 10 and 15 wt %). Detailed characterization of the films revealed the following: (i) they exhibited fibrous structures on their surfaces. The strong tendency of the linter cellulose chains to aggregate in LiCl/DMAc suggests that these fibrous elements consist of cellulose chains, as can be deduced from SEM images of the film of cellulose proper; (ii) the cellulose acetate films obtained from samples with DS 2.1 and 2.9 exhibited microspheres on the surface, whose formation seems to be favored for acetates with higher DS; (iii) AFM analysis showed that, in general, the presence of cellulose increased both the asperity thickness and the surface roughness of the analyzed films, indicating that cellulose chains are at least partially organized in domains and not molecularly dispersed between acetate chains; and (iv) the films prepared from cellulose and acetates exhibited lower hygroscopicity than the acetate films, also suggesting that the cellulose chains are organized into domains, probably due to strong intermolecular interactions. The linter and sisal acetates (the latter from a prior study), and their respective films, were prepared using the same processes; however, the two sets of films presented more differences (as in humidity absorption, optical, and tensile properties) than similarities (as in some morphological aspects), most likely due to the different properties of the starting materials. Potential applications of the films prepared in tissue engineering scaffold coatings and/or drug delivery are mentioned.
本文描述了由棉短绒纤维素及其相应醋酸酯制备薄膜的所得结果。乙酰化反应在LiCl/DMAc溶剂体系中进行。薄膜由醋酸纤维素（取代度，DS 0.8 - 2.9）与棉短绒纤维素（5%、10%和15%重量）的LiCl/DMAc溶液制备而成。对薄膜的详细表征显示如下：(i) 它们在表面呈现出纤维结构。棉短绒纤维素链在LiCl/DMAc中强烈的聚集倾向表明这些纤维元素由纤维素链组成，这可从纯纤维素薄膜的扫描电子显微镜图像中推断得出；(ii) 从取代度为2.1和2.9的样品获得的醋酸纤维素薄膜在表面呈现出微球，对于取代度较高的醋酸酯，微球的形成似乎更有利；(iii) 原子力显微镜分析表明，总体而言，纤维素的存在增加了所分析薄膜的粗糙度厚度和表面粗糙度，表明纤维素链至少部分地在区域中组织化，而非分子分散在醋酸酯链之间；以及(iv) 由纤维素和醋酸酯制备的薄膜比醋酸酯薄膜表现出更低的吸湿性，这也表明纤维素链组织成区域，可能是由于强烈的分子间相互作用。棉短绒和剑麻醋酸酯（后者来自先前的研究）及其各自的薄膜采用相同的工艺制备；然而，这两组薄膜呈现出更多的差异（如在吸湿、光学和拉伸性能方面）而非相似性（如在一些形态学方面），这很可能是由于起始材料的不同性质所致。文中提及了所制备薄膜在组织工程支架涂层和/或药物递送方面的潜在应用。
