细菌纤维素表面修饰及功能化
发布时间：2018-08-12 19:43
【摘要】：细菌纤维素(BC)是国际公认的一种优异的天然纳米生物材料,具有独特的精细三维网状结构,因其“纳米效应”而具有高比表面积、高吸水性及保水性、高气液透过率、高湿态强度等优异特性。目前BC膜材料已经实现规模化生产,主要应用于食品及医用领域,解决了静电纺纳米纤维产量低,难以工业化生产的难题,具有十分广泛的应用前景。但目前BC材料的研究主要集中在生物发酵优化以及低成本化方向,对于具有差异化结构性能的BC改性材料及其相关功能纳米材料的研究较少,而已报道的国内外关于BC功能材料的研究主要集中于增强及医用领域,其应用领域也有待进一步拓展。在BC衍生化及功能化过程中,其表面特性决定了BC的表面修饰方法选取与功能化复合体系的建立。而目前BC的性能研究大多集中在基础理化特性的表征,而对其表面特性的研究报道较少。 因此,本篇论文通过系统化研究BC表面特性,包括BC表面可及羟基数量,不同羟基的可及性及氢键有序程度,BC纤维表面电动力学行为等,从而更好地指导差异化BC改性材料及BC基功能化材料的设计及制备,理解BC纳米纤维在其中的模板作用以及纳米反应器效应。 根据性能及应用需求,探索BC改性材料的结构设计和制备技术,通过对BC纳米材料进行表面修饰,实现BC表面活性基团的可控设计；并进一步基于BC及其衍生化BC纳米纤维活性位点控制的原位制备机理,采用不同方法原位可控构筑新型BC基功能化纳米复合材料体系,为提高BC附加值,拓展BC在光电信息等新材料领域应用提供更为有效的方法和新的合成思路。 BC表面性能、表面修饰及功能化研究具体内容如下： 1.研究了BC表面羟基可及度及其形态结构与性能的关系,为BC表面修饰及功能化体系的拓展提供了理论依据。结果表明BC表面羟基可及数目为1.28(最大值为3),BC中O(2)H是三种羟基中最可及的,O(3)H最不可及,其与高度有序的O(3)H..O(5')分子内氢键一致。BC的等电势点pH为3.7,Splateau为-7.5mV。在中性及碱性条件下的BC模板效应最显著,其表面羟基基团的大量解离可使其作为有效的反应活性位点来控制纳米颗粒及纳米线材料的生长与分布。BC膜具有高比表面积(55.37m2/g),且其比表面积及其微观形态可以通过不同的干燥方式及后处理进行调控。 2.将BC优异表面特性与实际应用相结合,利用BC表面大量的可及性羟基基团以及比表面积的可调控性,将BC膜材料固定在石英晶体微天平(QCM)表面,制备了一种新颖的具有高稳定性和灵敏度的低成本湿度传感器。结果表明传感器展示了优异的传感特性,频移对数对相对湿度显示了线性关系,且基于BC膜的传感器在97%相对湿度时灵敏度比相应的纤维素膜增加了4倍多,所得传感器具有优异的可逆性及长期稳定性。 3.通过采用乙酰化及偕胺肟化学改性方法,以乙酰基团及胺肟基团部分取代BC纳米纤维表面大量的羟基官能团,拓展BC在疏水增强基体材料及金属离子吸附领域的应用前景。使用碘作为催化剂,通过绿色高效无溶剂方法对BC纳米纤维表面官能团进行乙酰化改性,制备的乙酰化BC膜具有良好的表面疏水性能及优异的机械性能(杨氏模量13.4GPa,拉伸强度225.8MPa),有利于作为疏水的非极性聚合物基体的增强材料。在保留BC聚集态结构和一定物理机械性能的同时制备了偕胺肟改性BC,有效地提高了金属离子的吸附容量,扩展并丰富了BC纳米纤维的模板效应。 4.利用BC纳米纤维表面大量的可及性羟基基团与所引入组分的相互作用,可以通过简单的表面修饰方法制备新颖的BC功能膜材料,有效拓展BC膜的应用领域。通过在BC表面引入NO2SP组分成功制备了一种新型的BC-NO2SP光致变色纳米纤维膜,该膜颜色可随着BC-NO2SP膜结构中吡喃组分的异构化发生可逆变化；通过在BC表面引入聚乙烯亚胺(PEI)组分进行表面修饰,成功制得了一种新颖、简单且可重复使用的PEI-BC纳米纤维膜基的QCM气体传感器,该传感器在室温下甲醛浓度1-100ppm范围内具有良好的线性,表现出高灵敏度,良好的可重复性和选择性,开创BC纳米纤维膜新的应用领域。 5.利用BC及偕胺肟BC(Am-BC)的活性位点控制的原位合成机理以及纳米反应器效应,成功制备了具有光催化特性的ZnO/BC, ZnO/Am-BC及光致发光特性的CdSe/BC纳米复合膜材料。结果表明所得复合膜结构性能受反应液浓度及反应时间的影响,在优化条件下,直径为20-50nm的ZnO及CdSe纳米粒子均匀分布在BC纳米纤维的表面。Am-BC中胺肟基团的引入为ZnO成核及生长提供了更多的有效活性位点,有效提高了ZnO纳米颗粒负载量。相同条件下(120min),ZnO/BC/及ZnO/Am-BC复合膜对甲基橙溶液的光催化降解效率分别可达70%及91%,可应用于有机污水处理,且易于回收,可循环利用。所得CdSe/BC柔性复合膜在紫外光激发下显示出均匀的绿色荧光,可应用于证券纸,传感器及柔性荧光膜材料等领域。 6.采用BC作为模板材料,利用BC表面大量羟基与苯胺中的胺基相互作用,过硫酸铵作为氧化剂,通过原位氧化聚合苯胺制备了新颖的PANI/BC柔性导电纳米复合膜。研究了反应时间,掺杂酸对纳米复合膜性能的影响。优化条件下,PANI颗粒均匀沉积在BC纳米纤维表面,沿着BC模板形成连续的直径为200nm的纳米鞘结构,该复合膜电导率可达5.0×10-2S/m,并具有优异的柔性及良好的机械性能(杨氏模量5.6GPa,拉伸强度95.7MPa),且对应力具有敏感性。该材料可应用在传感器,柔性电极,柔性显示材料及其它柔性导电膜等领域,同时本工作也为BC应用领域的拓展提供了新的方向。
[Abstract]:Bacterial cellulose (BC) is internationally recognized as an excellent natural nano-biomaterial with a unique fine three-dimensional network structure. Because of its "nano-effect", BC has many excellent properties, such as high specific surface area, high water absorption and water retention, high gas-liquid permeability, high wet strength and so on. In the field of food and medicine, it has solved the problem of low output of electrospun nanofibers, which is difficult to industrialize production, and has a very broad application prospect. However, at present, the research of BC materials mainly focuses on the optimization of bio-fermentation and low-cost direction. For BC modified materials with differentiated structure and properties and related functional nanomaterials. There are few studies on BC functional materials, but the research on BC functional materials at home and abroad mainly focuses on the field of reinforcement and medicine, and its application field needs to be further expanded. It is focused on the characterization of basic physical and chemical properties, but few reports have been reported on its surface characteristics.
Therefore, this paper systematically studies the surface properties of BC, including the number of accessible hydroxyl groups, the accessibility of different hydroxyl groups, the degree of hydrogen bonding order, and the surface electrodynamic behavior of BC fibers, so as to better guide the design and preparation of differentiated BC modified materials and BC-based functional materials, and to understand the template of BC nanofibers. And nano reactor effect.
According to the performance and application requirements, the structural design and preparation technology of BC modified materials were explored, and the controllable design of BC surface active groups was realized by modifying the surface of BC nano-materials; furthermore, based on the in-situ preparation mechanism controlled by the active sites of BC and its derivative BC nanofibers, novel BC in-situ controllable structures were constructed by different methods. The functionalized nanocomposites based on BCs provide more effective methods and new synthesis ideas for increasing the added value of BCs and expanding the application of BCs in the field of new materials such as optoelectronic information.
The details of surface properties, surface modification and functionalization of BC are as follows:
1. The relationship between the surface hydroxyl accessibility and the morphological structure and properties of BC was studied, which provided a theoretical basis for the surface modification of BC and the development of functional systems. The isoelectric potential of BC is 3.7 and Splateau is - 7.5 mV. In neutral and alkaline conditions, the template effect of BC is most significant. The dissociation of hydroxyl groups on the surface of BC can be used as an effective reactive site to control the growth and distribution of nanoparticles and nanowire materials. The area and its micro morphology can be regulated by different drying methods and post-processing.
2. A novel low-cost humidity sensor with high stability and sensitivity was fabricated by combining the excellent surface properties of BC with the practical application, using a large number of accessible hydroxyl groups on the surface of BC and the controllability of specific surface area. The sensitivity of the sensor based on BC membrane at 97% relative humidity is more than four times higher than that of the corresponding cellulose membrane. The sensor has excellent reversibility and long-term stability.
3. By using acetylation and amidoxime chemical modification methods, a large number of hydroxyl groups on the surface of BC nanofibers were partly substituted by acetyl group and amidoxime group, and the application prospects of BC in hydrophobic reinforced matrix materials and metal ion adsorption were expanded. The surface of BC nanofibers was modified by green and solvent-free method using iodine as catalyst. Acetylated BC films with good surface hydrophobic properties and excellent mechanical properties (Young's modulus 13.4GPa, tensile strength 225.8MPa) were prepared by acetylation modification of surface functional groups, which was beneficial to the reinforcement of hydrophobic non-polar polymer matrix. Oxime modified BC can effectively improve the adsorption capacity of metal ions, and expand and enrich the template effect of BC nanofibers.
4. Using the interaction between a large number of accessible hydroxyl groups on the surface of BC nanofibers and the components introduced, novel BC functional membranes can be prepared by simple surface modification methods, which can effectively expand the application fields of BC membranes. A novel, simple and reusable QCM gas sensor based on PEI-BC nanofiber membrane was successfully fabricated by introducing polyethylenimide (PEI) onto the surface of BC-NO2SP membrane to modify the color of the film reversibly with the isomerization of pyran components. With good linearity, high sensitivity, good repeatability and selectivity, BC nanofiber membranes have opened up new applications.
5. The photocatalytic properties of ZnO/BC, ZnO/Am-BC and CdSe/BC nanocomposite films were successfully prepared by the in-situ synthesis mechanism controlled by the active sites of BC and amidoxime BC (Am-BC) and the effect of nanoreactor. The results showed that the structure and properties of the films were affected by the concentration of the reaction solution and the reaction time. ZnO and CdSe nanoparticles with diameters of 20-50 nm were uniformly distributed on the surface of BC nanofibers under chemical conditions. Aminoxime groups in Am-BC provided more active sites for the nucleation and growth of ZnO and effectively increased the loading of ZnO nanoparticles. Under the same conditions (120 min), ZnO/BC/ZnO/Am-BC composite films photocatalyzed methyl orange solution. CdSe/BC flexible composite membrane exhibits uniform green fluorescence excited by ultraviolet light and can be used in securities paper, sensors and flexible fluorescent membrane materials.
6. A novel PANI/BC flexible conductive nanocomposite film was prepared by in-situ oxidation polymerization of aniline with ammonium persulfate as oxidant. The effects of reaction time and doping acid on the properties of the nanocomposite film were studied. The composite film has excellent flexibility and mechanical properties (Young's modulus 5.6 GPa, tensile strength 95.7 MPa) and is sensitive to stress. It can be used in sensors, flexible electrodes, and flexible. Display materials and other flexible conductive films, and this work also provides a new direction for the development of BC applications.
【学位授予单位】：东华大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：R318.08;TB383.1
本文编号：2180155
[Abstract]:Bacterial cellulose (BC) is internationally recognized as an excellent natural nano-biomaterial with a unique fine three-dimensional network structure. Because of its "nano-effect", BC has many excellent properties, such as high specific surface area, high water absorption and water retention, high gas-liquid permeability, high wet strength and so on. In the field of food and medicine, it has solved the problem of low output of electrospun nanofibers, which is difficult to industrialize production, and has a very broad application prospect. However, at present, the research of BC materials mainly focuses on the optimization of bio-fermentation and low-cost direction. For BC modified materials with differentiated structure and properties and related functional nanomaterials. There are few studies on BC functional materials, but the research on BC functional materials at home and abroad mainly focuses on the field of reinforcement and medicine, and its application field needs to be further expanded. It is focused on the characterization of basic physical and chemical properties, but few reports have been reported on its surface characteristics.
Therefore, this paper systematically studies the surface properties of BC, including the number of accessible hydroxyl groups, the accessibility of different hydroxyl groups, the degree of hydrogen bonding order, and the surface electrodynamic behavior of BC fibers, so as to better guide the design and preparation of differentiated BC modified materials and BC-based functional materials, and to understand the template of BC nanofibers. And nano reactor effect.
According to the performance and application requirements, the structural design and preparation technology of BC modified materials were explored, and the controllable design of BC surface active groups was realized by modifying the surface of BC nano-materials; furthermore, based on the in-situ preparation mechanism controlled by the active sites of BC and its derivative BC nanofibers, novel BC in-situ controllable structures were constructed by different methods. The functionalized nanocomposites based on BCs provide more effective methods and new synthesis ideas for increasing the added value of BCs and expanding the application of BCs in the field of new materials such as optoelectronic information.
The details of surface properties, surface modification and functionalization of BC are as follows:
1. The relationship between the surface hydroxyl accessibility and the morphological structure and properties of BC was studied, which provided a theoretical basis for the surface modification of BC and the development of functional systems. The isoelectric potential of BC is 3.7 and Splateau is - 7.5 mV. In neutral and alkaline conditions, the template effect of BC is most significant. The dissociation of hydroxyl groups on the surface of BC can be used as an effective reactive site to control the growth and distribution of nanoparticles and nanowire materials. The area and its micro morphology can be regulated by different drying methods and post-processing.
2. A novel low-cost humidity sensor with high stability and sensitivity was fabricated by combining the excellent surface properties of BC with the practical application, using a large number of accessible hydroxyl groups on the surface of BC and the controllability of specific surface area. The sensitivity of the sensor based on BC membrane at 97% relative humidity is more than four times higher than that of the corresponding cellulose membrane. The sensor has excellent reversibility and long-term stability.
3. By using acetylation and amidoxime chemical modification methods, a large number of hydroxyl groups on the surface of BC nanofibers were partly substituted by acetyl group and amidoxime group, and the application prospects of BC in hydrophobic reinforced matrix materials and metal ion adsorption were expanded. The surface of BC nanofibers was modified by green and solvent-free method using iodine as catalyst. Acetylated BC films with good surface hydrophobic properties and excellent mechanical properties (Young's modulus 13.4GPa, tensile strength 225.8MPa) were prepared by acetylation modification of surface functional groups, which was beneficial to the reinforcement of hydrophobic non-polar polymer matrix. Oxime modified BC can effectively improve the adsorption capacity of metal ions, and expand and enrich the template effect of BC nanofibers.
4. Using the interaction between a large number of accessible hydroxyl groups on the surface of BC nanofibers and the components introduced, novel BC functional membranes can be prepared by simple surface modification methods, which can effectively expand the application fields of BC membranes. A novel, simple and reusable QCM gas sensor based on PEI-BC nanofiber membrane was successfully fabricated by introducing polyethylenimide (PEI) onto the surface of BC-NO2SP membrane to modify the color of the film reversibly with the isomerization of pyran components. With good linearity, high sensitivity, good repeatability and selectivity, BC nanofiber membranes have opened up new applications.
5. The photocatalytic properties of ZnO/BC, ZnO/Am-BC and CdSe/BC nanocomposite films were successfully prepared by the in-situ synthesis mechanism controlled by the active sites of BC and amidoxime BC (Am-BC) and the effect of nanoreactor. The results showed that the structure and properties of the films were affected by the concentration of the reaction solution and the reaction time. ZnO and CdSe nanoparticles with diameters of 20-50 nm were uniformly distributed on the surface of BC nanofibers under chemical conditions. Aminoxime groups in Am-BC provided more active sites for the nucleation and growth of ZnO and effectively increased the loading of ZnO nanoparticles. Under the same conditions (120 min), ZnO/BC/ZnO/Am-BC composite films photocatalyzed methyl orange solution. CdSe/BC flexible composite membrane exhibits uniform green fluorescence excited by ultraviolet light and can be used in securities paper, sensors and flexible fluorescent membrane materials.
6. A novel PANI/BC flexible conductive nanocomposite film was prepared by in-situ oxidation polymerization of aniline with ammonium persulfate as oxidant. The effects of reaction time and doping acid on the properties of the nanocomposite film were studied. The composite film has excellent flexibility and mechanical properties (Young's modulus 5.6 GPa, tensile strength 95.7 MPa) and is sensitive to stress. It can be used in sensors, flexible electrodes, and flexible. Display materials and other flexible conductive films, and this work also provides a new direction for the development of BC applications.
【学位授予单位】：东华大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：R318.08;TB383.1
【引证文献】
相关硕士学位论文 前3条
1 刘晖;细菌纤维素基复合材料的制备及性能研究[D];南京林业大学;2016年
2 邢雪宇;细菌纤维素/明胶复合多孔支架的制备及性能研究[D];东华大学;2016年
3 王紫蓉;固态细菌纤维素的制备及结构研究[D];华南理工大学;2016年
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