Study On The Structure,Properties And Application Of Carboxymethyl Cellulose Based Fluorescent Hydrogel

Rare earth polymer fluorescent hydrogels are flexible,biocompatible,responsive to shape,volume and fluorescence color changes,and have great application potential in intelligent fields such as sensing,biological imaging,and anti-counterfeiting encryption.Carboxymethyl cellulose（CMC）is a polyanionic cellulose derivative containing a large number of hydroxyl groups,which has excellent water solubility and environmental friendliness.It is widely used in food,biomedicine,textile and paper industries.Polyvinyl alcohol（PVA）is a medical material approved for clinical use by the Food and Drug Administration.It has excellent biocompatibility and hydrophilicity,and is an excellent modifiable hydrogel matrix.In this paper,CMC-Eu（Ⅲ）and/or CMC were integrated into PVA matrix to prepare composite hydrogel materials.The structure and thermal properties of composite hydrogels were characterized and analyzed,and the swelling properties,mechanical properties and fluorescence properties of the hydrogels were studied.In addition,the prepared composite hydrogel was added into the pulp to prepare fluorescent paper.This work expanded the high-value utilization channel of renewable cellulose resources under the premise of sustainable development concept of green chemistry.The main conclusions of this paper are as follows:（1）Through SEM and BET analysis,the CMC-Eu（Ⅲ）/PVA（CEP）composite hydrogel formed a physical cross-linked porous network cross-linked structure.And the distribution of the mesopores was similar to that of PVA hydrogel（average diameter was 2.70 nm）,but the addition of an appropriate amount of CMC-Eu（Ⅲ）would make the pore distribution of the hydrogel orderly and fiber interwoven.Through XRD and DSC analysis,compared with PVA hydrogel,the crystallinity of CEP composite hydrogel showed a slight decrease,and the crystal size could be reduced from 5.47 nm to 3.28 nm at the minimum.Combined with the change in the absorption peaks of the FT-IR,it proved that the unreacted hydroxyl group in CMC-Eu（Ⅲ）has hydrogen bonding with the hydroxyl group,entanglement,and van der Waals forces on the PVA chain.These forces and network structure enhanced mechanical properties of CEP composite hydrogel.The breaking strain of the CEP-5 was 112%,which was 37 times that of PVA.The maximum tensile strength of CEP-10 was 44.91±2.69 k Pa,which was about 2 times that of PVA.It also could also maintain the high-water content about90%and 611.54%of swelling ratio（SR）.By adding CEP composite hydrogel in the pulp to bamboo pulp for papermaking,when the content of CEP-15 composite hydrogel was 1%,the binding effect with bamboo pulp fiber was better.It emitted Eu³⁺characteristic strong fluorescence at 615 nm,and enhanced the tensile strength（3.52 k N/m）,elongation at break（1.598%）and burst strength（201 k Pa）of fluorescent paper.The fluorescent CEP composite hydrogel prepared in this experiment could be used as a internal sizing agent without changing the process and equipment.The fluorescent functional paper could be used in the field of security and anti-counterfeit paper.（2）Within the scope of this experiment,CMC-Eu（Ⅲ）/CMC/PVA（CECP）composite hydrogels emitted the characteristic red fluorescence of Eu³⁺.Although its fluorescence intensity was affected by factors such as crystallinity and CMC content,the pore size and distribution of CECP composite hydrogels were the most important factors affecting the fluorescence intensity at ⁵D₀→⁷F₂.After adding CMC,the network structure of the CECP hydrogel became loose,and the water swelling property was enhanced,up to 1403.70%.In addition,CECP composite hydrogel was swelling responsive to p H.Compared with S1,the SR of S2～S6 with CMC at p H=2.1 and 12.2 were significantly lower than that of water at p H 6.8.The S5 was the most significant,and the SR were 1071.05%（p H=6.8）,526.67%（p H=2.1）,302.94%（p H=12.2）,respectively.All CECP composite hydrogels had the smallest swelling at p H=12.2,and their tensile mechanical properties are the strongest.The CECP composite hydrogel prepared in this experiment was insoluble in an acid-base environment,still had good strength and flexibility,which could meet the requirements of p H environments multifunctional applications.