二醋酸纤维素接枝聚己内酯的核磁共振表征

用^1H-NMR和^13C-NMR研究了二醋酸纤维素(CDA)和聚己内酯(PCL)的接枝共聚反应,确定了^1H-NMR和^13C-NMR谱中各谱峰的归属,为证明二醋酸纤维素和己内酯的接枝共聚反应提供了依据。     

Synthesis of cellulose benzoates under homogeneous conditions in an ionic liquid

The ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl) as a reaction medium was studied for the synthesis of cellulose benzoates by homogeneous acylation of dissolved cellulose with benzoyl chlorides in the absence of any catalysts. Cellulose benzoates with a degree of substitution (DS) in the range from about 1 to 3.0 were accessible under mild conditions. The DS of cellulose derivatives increased with the increase of the molar ratio of benzoyl chloride/anhydroglucose unit (AGU) in cellulose, reaction time, and reaction temperature. Benzoylation of cellulose with some 4-substituted benzoyl chlorides including 4-toluoyl chloride, 4-chlorobenzoyl chloride and 4-nitrobenzoyl chloride was also readily carried out under mild conditions. Furthermore, regioselectively substituted mixed cellulose esters were synthesized in this work. All products were characterized by means of FT-IR, ¹H-NMR, and ¹³C-NMR spectroscopy. In addition, at the end of benzoylation of cellulose, the ionic liquid AmimCl was easily recycled. When the recycled AmimCl was used as the reaction media, the cellulose benzoate with a similar DS was obtained under comparable reaction conditions.     

Metal adsorption of carboxymethyl cellulose/carboxymethyl chitosan blend hydrogels prepared by Gamma irradiation

Blend hydrogels based on the carboxymethyl cellulose (CMC) and carboxymethyl chitosan (CMCts) were prepared by γ-irradiation of a high concentrated CMC/CMCts aqueous solution. Properties of the hydrogels, such as gel fraction, swelling ratio, gel strength, and metal adsorption for Pb and Au were investigated. The gel fraction increased with increasing dose, while the swelling ratio decreased with increasing it. The obtained blend hydrogels had high adsorption performance which was controlled by adjusting the composition of CMC/CMCts.     

磷酸化P-mCMC/mCS双极膜的制备及其性能的研究

以五氧化二磷,磷酸三乙酯和磷酸为反应剂,制备了磷酸化羧甲基纤维素(CMC),经Fe³⁺改性后用作为阳膜;以壳聚糖(CS)和聚乙烯醇共混物用戊二醛改性后用作为阴膜溶胶,将阴膜溶胶流延于阳膜上,制备了P-mCMC/mCS双极膜。测定了CS、CMC胶体的电荷密度,离子透过率,P-mCMC/mCS双极膜的红外光谱与离子交换能力。IR与接触角测定的结果表明,CMC经改性后其亲水性能得到了显著提高。膜交流阻抗、I-V工作曲线的测定结果表明该双极膜阻抗及工作电压均较小。     

纤维素微孔锂电隔膜的制备及性能研究

为了改善锂电隔膜的亲液性和耐高温性,以醋酸纤维素为成膜材料,利用相转化法制备了新型锂电隔膜,通过形貌和孔道结构表征、亲液性能和耐热性能测试对醋酸纤维素隔膜的基本性能进行研究,并将该隔膜装配成锂离子电池进行充放电性能测试. 结果表明,醋酸纤维素隔膜具有均匀的微孔结构,孔隙率达到65%,约为传统聚烯烃隔膜的1.5倍;纤维素材料的良好亲液性和高孔隙率结构改善了隔膜的吸液性能,其吸液率达到285%;该隔膜在150 ^oC、30 min的热处理条件下未发生明显的热收缩. 鉴于上述优点,相对于市售PE隔膜,醋酸纤维素隔膜所装配锂离子电池显示出更优的循环性能和倍率性能.     

近红外漫反射光谱法测定天然纤维素浆粕聚合度

提出一种采用近红外光谱测定天然纤维素(棉、木)浆粕聚合度的方法。实验收集了195个天然纤维素浆粕样品,采用GB/T 9107-1999方法测定了其聚合度,对样品进行粉碎预处理后,放入旋转杯中采集相应的近红外漫反射光谱。通过化学计量学偏最小二乘方法(PLS)将聚合度数据与近红外光谱关联,分别建立了棉木浆粕混合样品、棉浆粕样品和木浆粕样品的聚合度定量模型。最优模型相关系数分别为0.980,0.993,和0.886,预测均方根误差(RMSEP)分别为147,143和53。研究了近红外方法精密度和准确性。结果表明棉浆粕和木浆粕分类模型预测准确性优于混合模型,且其预测精密度符合国标(GB)方法要求。另外,采用主成分分析方法建立了棉浆粕和木浆粕的识别模型,结果表明该模型可以有效识别棉浆粕和木浆粕。该方法操作简单、分析速度快,能够满足天然纤维素浆粕聚合度在线检测要求,为实现清洁制浆新工艺聚合度在线监控目标提供了理论和技术依据。     

自组装辅助聚合法制备纤维素基温度/pH双敏感性荧光纳米凝胶

通过自组装辅助的一步法制备了具有温度和pH双重响应性的荧光纳米凝胶(FNG). 首先设计制备了一种水溶性含双键的荧光单体5-丙烯酰胺荧光素(5-AAF), 在水溶性纤维素醚——羟丙基纤维素(HPC)主链上引发5-AAF的接枝共聚, 同时由于5-AAF的疏水作用力诱导共聚物发生自组装, 并通过双官能团交联剂亚甲基二丙烯酰胺(MBA)的加入使自组装纳米聚集体交联, 从而一步制得具有环境响应性的FNG, 该过程在水相中进行, 具有高效、 “绿色”的优点. 研究结果表明, 改变合成过程中HPC的分子量可调控所得FNG的环境响应性. 对FNG环境响应性的研究表明, FNG链段上的亲疏水基团及与水分子间的氢键作用是影响凝胶温度响应性的主要因素. 此外, FNG的荧光在中性及碱性溶液中显著加强, 在酸性溶液中迅速猝灭. 由于FNG的荧光信号对温度和pH的显著敏感性, 且具有较低的细胞毒性, 因此在荧光标记生物检测及生物微环境的温度/pH检测等领域具有广泛的应用前景.     

苝酰亚胺接枝纤维素的合成与染料吸附性能

合成了一种新型苝酰亚胺接枝纤维素材料3,通过元素分析、红外、扫描电子显微镜等技术手段证明了其结构。 染料吸附实验表明其对所测试的4种染料分子（橙黄G,亮丽春红,亚甲基蓝和结晶紫）均有较好的吸附能力,吸附容量分别达到1.04、1.21、1.14和0.96 mmol/g。 吸附过程符合拟二阶动力学模型和Langmuir等温方程,吸附过程是自发放热的。 在pH值2~12范围内,聚合物3的吸附性能保持基本稳定。 由吸附实验结果推测,静电作用、氢键和π-π堆积均在吸附过程中有重要作用。     

Bio-Based Nanocomposites of Cellulose Acetate and Nano-Clay with Superior Mechanical Properties

Summary: Bio-based nanocomposites were manufactured by melt intercalation of nanoclays and cellulose acetate (CA) with and without plasticizer. Glycerol triacetate (triacetin) as plasticizer up to 30 mass%, and different types of organo-modified and unmodified montmorillonites (MMTs) as filler were used. X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM), were used to study clay dispersion, intercalation/exfoliation, and structure of the composites. XRD and TEM revealed very good dispersion and exfoliation of modified clay throughout the CA matrix. While for unmodified clay agglomeration and poor dispersion but an intercalated structure was observed. The mechanical properties of injection moulded test bars were determined by a tensile experiment giving tensile strength, Young's modulus and elongation at break. Adding plasticizer facilitated the processing and up to 20 mass%, increased the tensile strength, Young's modulus and elongation at break as well. Higher amount of plasticizer diminished the tensile properties except elongation showing a slight increase. In all plasticized composites, organo-modified clay improved the tensile strength and at the same time, young's modulus and elongation almost remained constant. On the other hand, plasticized CA compounded with unmodified clay revealed lower properties. In a particular case, compounding of unplasticized CA with unmodified clay resulted in superior mechanical properties with a novel structure. So that, in optimum percentage –5 mass%- of unmodified clay, tensile strength and young's modulus increased significantly by 335% and 100%, to 178 MPa and 8.4 GPa, respectively. This is a dramatic improvement in strength and stiffness of CA. Adding organo-modified clay resulted in a little improvement in tensile properties. SEM pictures of the optimum composite showed a core/shell structure with high orientation in the shell part. It is supposed that this behaviour is caused by the interaction between CA hydroxyl groups and free cations existing in the galleries of unmodified clay.     

Unconventional Reactivity of Cellulose Dissolved in Ionic Liquids

Summary: Ionic Liquids (IL) were applied as solvent and reaction medium in the field of homogeneous cellulose chemistry. Whereas investigations on tosylation and nucleophilic displacement reactions lead to unexpected products the application of the Huisgen reaction was successful. The standard conditions for tosylation of cellulose using the IL 1-ethyl-3-methylimidazolium acetate (EMImAc) as solvent lead exclusively to cellulose acetate, due to activation of the acetate ion of the IL by forming a mixed anhydride with p-toluenesulfonyl chloride. Further investigations showed that the anions of EMImAc and 1-ethyl-3-methylimidazolium chloride (EMImCl) are able to act as nucleophiles, thus substituting tosyl groups of tosylcellulose and forming unexpected products. Using EMImAc as solvent first to third generation propargyl-polyamidoamine (PAMAM) dendrons were attached to 6-azido-6-deoxy cellulose (degree of substitution, DS 0.75) utilising the copper catalysed Huisgen reaction leading to novel dendronized cellulose derivatives with DS values of up to 0.60. Detailed structure characterisation of the products, including elemental analysis, FTIR and NMR spectroscopy, indicates that the synthesis approach leads to products without impurities or remaining IL.