Construction Of Functional Polysaccharide Materials On The Basis Of Surface And Interface Interactions

Biomimetic and biomedical materials have become one of the international frontiers. Lotus leaf and cicada wing inspired self-cleaning materials, onion inspired multi-layered hydrogels and tough bone inspired tissue engineering scaffolds have attracted more and more attentions. Such extraordinary biomimetic and biomedical materials are associated with their unique micro structures on the surface and interface as well as the interaction. Cellulose and chitin are the most abundant bio mass resources on earth, and they belong to carbohydrate polymers, generally known as the natural polysaccharides. They exhibit characteristics of safe, nontoxic, biocompatible and biodegradable, so they are ideal raw materials for the construction of biomimetic and biomedical functional materials.Utilizing cellulose and chitin as raw materials, novel functional materials were fabricated directly from solutions through non covalent bond interaction as well as surface and interface interaction in this work, which were dissolved in alkli/urea aqueous solutions at low temperature, respectively. Meanwhile, the structure and properties of materials were characterized by solid state13C NMR, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), water contact angle measurement, rheological measurements, thermogravimetric analysis (TGA), UV-vis spectroscopy(UV), photoluminescence spectra (PL) and mechanical testing. The correlation between structure and properties as well as surface and interface interaction was also studied. Meanwhile, the potential application in biomedical fields was also evaluated by biological experiments. Thus, it could develop novel pathways by using polysaccrides for the construction of a series of biopolymer-based functional materials.The innovation of this work was listed as follows:(1) Biocompatible cellulose/hydroxyapatite nanocomposite films were constructed and nano hydroxyapatite particles (nHAP) were dispersed evenly as a result of the interfacial hydrogen bonding interaction between hydroxyapatite and cellulose;(2) Cellulose/SiO2nanocomposite films were constructed through two-phase interfacial interaction, and the corresponding moisture responsive mechanism was clarified;(3) Based on the hydrophilic-hydrophobic interfacial interaction, the micro and submicron pores of cellulose gel sheets were used for the first time to control the stearic acid and12-Hydroxyoctadecanoic acid (HOA) crystals grow orderly for the fabrication of high hydrophobic cellulose films and hair growth inspired "self-cleaning" fluorescent cellulose films;(4) High strength and biocompatible multi-layered cellulose hydrogels were successfully constructed by the fast contact of solid-liquid interface;(5) Based on the interfacial interaction between chitin and poly(vinyl alcohol)(PVA) as well as hydroxyapatite, high strength chitin/PVA composite hydrogels and chitin/HAP plastics with excellent biocompatibility were constructed.The primary contents and conclusions of this work can be divided into seven parts.The nHAP were successfully incorporated into the cellulose matrix in NaOH/urea aqueous solvent through a simple and low cost method. The TEM and FTIR results demonstrated that the strong hydrogen bonding force induced the tight fixation and homogenous dispersion of nHAP (20-40nm) in the cellulose film, forming organic/inorganic hybrid films with primary hydroxyapatite size. The nHAP exhibited good crystallinity in the cellulose film. The mechanical strength and thermal stability increased with the incorporation of nHAP. Especially, the293T cell culture experiment demonstrated that the hybrid films exhibited nontoxicity and good biocompatibility. Therefore, they would have potential application as bone repairing materials in the biomedical field.Based on the hydrogen bonding interaction among SiO2, water and cellulose, SiO2nanoparticles were introduced into the cellulose matrix, forming organic/inorganic hybrid films through coagulation and regeneration. The strong hydrogen bonding interaction induced the homogenous dispersion of SiO2in the cellulose matrix, displaying good compatibility. The results of transmittance and mechanical property revealed that the SiO2nanoparticles increased the mechanical property and transparency of cellulose hydrogels as well as the mechanical property of cellulose film. Especially, the cellulose/SiO2nanocomposite film displayed milky color at dry state and changed to transparent film when it was soaked into water. The structure analysis demonstrated that the SiO2, water and cellulose could form hydrogen bonding with the existence of abundant water to create uniform network structure, resulting in the increase of compatibility and transmittance. This kind of cellulose/SiO2smart composite film exhibited moisture responsive property, showing potential application in moisture and solvent detection.Stearic acid is a natural product, and it is biodegradable. Stearic acid crystals could grow controllably on the cellulose film by using the porous structure of regenerated cellulose gels through the solvent-vaporized induced crystallization method. The stearic acid crystals were fixed in the pores of the cellulose matrix tightly, and the controllable stearic acid crystallization was induced by the pore wall to form plate-like micro crystals with a micronano binary structure, resulting in high surface roughness. The results of XRD、SEM and water contact angle measurements demonstrated that vertical microplate-like stearic acid crystals could distribute evenly on cellulose film surface, the interspaces among the crystals could trap abundant air for the improvement of hydrophobicity. Therefore, the cellulose/stearic acid films were highly hydrophobic, biodegradable, safe, and inexpensive, showing potential applications in biodegradable waterproof packaging.Based on hydrophilic-hydrophobic interfacial interaction, HOA crystals could grow orderly and vertically in the submicron cavities of cellulose, resembling "hair growth" The porous cellulose matrix supplied not only cavities for the HOA crystals fixation, but the incompatibility between hydrophilic shells and hydrophobic HOA also favored the longitudinal and isolated growth of the HOA crystals, forming orderly "short hair" like crystals. The HOA with a few hydroxyls on the tail end could form hydrogen bonds with cellulose to be fixed in the cellulose matrix. The hydrophobic-hydrophilic interfacial interaction could induce the growth of the relatively hydrophobic HOA crystals along the pore wall of the hydrophilic cellulose separately, which exhibited a smooth surface. The HOA crystal morphologies can be controlled by changing the temperature and HOA concentration, and the perfect wormlike crystals could be fabricated at the suitable experimental conditions. The cellulose/HOA submicron composite films exhibited high hydrophobicity with self-clean ability. Especially,4-(1,2,2-triphenylethenyl) benzoic acid,(TPE-COOH) could interact with HOA through hydrophobic interaction to migrate onto the cellulose film surface and aggregate to emit, so the bifunctional photoluminescent and hydrophobic cellulose/HOA/TPE-COOH films were constructed. Thus, it would open up a novel one-step pathway to facilely design bio-inspired materials in the porous cellulose matrix by utilizing natural products, to resemble "hair growth" on the animal skin in the nature.Onion-like and multi-layered tubular cellulose hydrogels were constructed successfully through a fast contact of the solid-liquid interface between the gel spheres and rods loaded with acid and the cellulose solution. Due to the instant destruction of the cellulose inclusion complex (IC) by contact with acid on the surface of the gel core, the cellulose hydrogel layer could be constructed rapidly along the gel surface through the quick self-aggregation between cellulose chains. The layer thickness and inter-layer space could be controlled by adjusting the cellulose concentrations, the gel core diameter and the contacting time of the solid-liquid interface. Meanwhile, the multi-layered cellulose hydrogels exhibited relative high compressive strength, as a result of the relatively close packing of the cellulose chain bundles. The hydrogels had good architectural stability and solvent resistance against ethanol, acetone, Dimethylacetamide (DMAc) and NaOH aqueous solution. The biological experiment demonstrated that the L929cells could adhere and proliferate on the surface of the layers and in the inter-layer space, showing non-cytotoxicity and good biocompatibility. The controllable architecture and layer size of the multi-layered cellulose hydrogels are important in the application as biomedical materials.Novel chitin/PVA gels with high strength and excellent biocompatibility were fabricated by partially chemical crosslinking and treating with freezing-thawing process to induce the formation of PVA crystals and the intermolecular hydrogen bonds. When PVA content was25wt%for RCP75hydrogel, a regular jellyfish gel-like structure occurred, as a result of the formation of a dense packing pore wall consisted of chitin and PVA chains as well as the intermolecular hydrogen bonds to form oriented arrangement. The results of solid13C NMR、XRD and SEM revealed that the repeated freezing/thawing cycles induced a dense packing of physically and chemically crosslinked chains between chitin and PVA, enhanced intermolecular hydrogen bonding as well as a phase separation caused by the crystalline ice and the PVA crystals of the composite gels, leading to the layered porous structure. The mechanical properties of RCP75were improved rapidly and much higher than the other RCP gels and pure chitin gels, as a result of the broadly dispersed stress near a crack tip caused by the layered porous structure with bi-crosslinked networks. Furthermore, the chitin/PVA hydrogel had excellent biocompatibility and safety. The chitin/PVA hydrogels will be of considerable interest for utilizations in the biomedical field, because its biocompatibility and biodegradability could appropriately meet the requirement of tissue engineering.Based on hydrogen bonding interaction among chitin chains with exposed hydroxyl groups during the vacuum drying process, condensation occured and chitin molecules rearranged along the plane in all directions and packed tightly to create new aggragation states, so a new class of chitin plastic was constructed successfully by changing the shape and size. Meanwhile, hydroxyapatite particles were in situ synthesized in chitin matrix on the basis of its porous structure and good metal ions adsorption ability. There was strong interaction between chitin and hydroxyapatite, thus the mechanical property of chitin composite plastic was improved by the introduction of hydroxyapatite. Especially, MC3T3-E1cell culture experiments proved that the introduction of hydroxyapatite significantly improved the cell adhesion ability and promoted the proliferation ability. Therefore, the composite plastic had application prospect as bone repairing material in biomedical field.This thesis developed a series of cellulose and chitin functional materials by using alkali/urea aqueous solvents at low temperature, and the relationships between the structure and properties of materials as well as the surface and interface interaction were clarified. Thus, it could provide novel ideas and methods for the construction of high hydrophobic cellulose film,"self-cleaning" fluorescent cellulose film, high strength and biocompatible multi-layered cellulose hydrogels, high strength chitin composite hydrogels as well as chitin/inorganic composite plastic. These basic researches exhibit obvious creativity and academic value, and are in accordance with national sustainable strategy. Therefore, this thesis exhibits scientific significance and application prospect.