Synthesis And Properties Of Environment-sensitive Hydrogels Containing Lignocellulosic Components

Lignin,cellulose,hemicellulose are three main components of lignocellulose.New material has some specific function by introducing lignocellulose or its components into polymers in particular way,grafting-copolymerization and crosslinking,blending,interpenetrating net for instance.Different hydrogels had been synthesized using lignocellulosic components,and effects of lignocellulosic characteristics on the properties of hydrogels had been researched.Studies about cellulose-containing hydrogels have been done in depth,but hydrogels containing lignin or hemicellulose still need to be studied further.In this paper,lignocellulosic components including lignin,hemicellulose and lignincarbohydrate complex were introducing in PNIPAAm to prepare thermosensitive hydrogelsthrough graft-copolymerization and crosslinking.Thermosensitivity,thermostability,swelling ratios of hydrogel were studied,the relationship between lignocellulose structure and hydrogel properties was discussed.Milled wood lignin(MWL)from Eucalyptus,Indulin AT(alkali lignin,from softwood)and industrial alkali lignin from eucalyptus were used.MWL was some similar to original lignin in structural characteristics and existential state,it can be seen as unreacted lignin in lignocellulosic material.Indulin AT(from softwood)and lignin Leu(from hardwood)were same in isolating methods,but different in wood source.The properties of Indulin AT-containing hydrogel were discussed comparing with the hydrogel containing MWL in order to study the characteristic effects of lignin from same methods but different wood on properties of hydrogels.MWL and Leu were same in wood source,but different in isolating methods.The properties of Leu-containing hydrogel were discussed comparing with the hydrogel containing MWL in order to study the characteristic effects of lignin from same wood but different methods on properties of hydrogels.The lignin component in Lignin-carbohydrate complex(LCC)were some similar to original lignin in structural characteristics and existential state.was Fenton oxidized in order to enhance its reactive activity.Difference in structural characteristics of Indulin AT and its oxidized production(OAT),and difference in properties of hydrogels showed be focused on,this helped to understand the relationship of lignocellulosic components and properties their hydrogels.Results demonstrated that the properties of hydrogel were significantly influenced by the introducing of lignin,but the thermosensitivity of hydrogel did not change obviously,the lower critical solution temperature(LCST)of the hydrogels were still about 32?.Introducing of lignin did not alter the thermostability of hydrogel.SEM picture indicated that hydrogels containing lignin showed porous structure,and the size of pore was independent on dosage of lignin.A temperature sensitive hydrogel was prepared from lignin-carbohydrate complexes(LCC)and NIPAAm.Synthesis and properties of hydrogels were researched using MWL-containing hydrogel as control.Data manifested that reaction temperature,dosages of monomer and initiator had different influence on yields and equilibrium swelling ratios of hydrogels.Introducing of lignin or MWL all did not change the thermosensitivity of hydrogel significantly,the LCSTs of the hydrogels were all still about 32?.Comparing wih hydrogels containing MWL,swelling property of LCC-containing hydrogels were inhanced significantly.The swelling property of LCC-containing hydrogels were enhanced significantly when comparing wih hydrogels containing MWL,.The equilibrium swelling ratios(SRe)differed with different temperature,and slowed down with the temperature rising.The SRe at 25? had the value of 19.5 when the dosage of LCC was 1:12.Scanning electron microscope(SEM)pictures revealed that hydrogels containing LCC showed porous structure,and the size of pore increased with dosage of LCC.Indulin AT was modified by Fenton oxidation reaction,the product(OAT)was grafted onto PNIPAAm to synthesized OAT-containing hydrogels.Results demonstrated that dosage of OAT did not influence the thermostability of hydrogel significantly.Swelling ratios of the hydrogel rose up with the time,but the SRe reduced when temperature rising up.SEM pictures showed that hydrogels containing lignin were porous.This hydrogel was expected to be used in adsorption of harmful substances.A pH-and temperature-sensitive hydrogel was prepared by grafting copolymerization using modified hemicellulose as crosslinker and NIPAAm/ itaconic acid(IA)as monomers.The results proved that SRe,LCST and water retention were all increased with the dosage of IA.When the weight ratio of NIPAAm and IA(NIPAAm/IA)ranged between 96/4~98/2,LCSTs of hydrogels had the value of 36-38?.The simulative release of drug showed salicylic acid was released quickly from hydrogels in 1 h in simulated gastric fluid(p H1.5)and reached to equilibrium in 2.5 h.But salicylic acid was released slowly in simulated intestinal fluid(pH7.4).Cytotoxicity assay revealed that this kind of hemicellulose hydrogel was biocompatibility,and prospected to be utilized in drug delivery system.Behavior of absorbing methylene blue(MB)was discussed.Data investigated that the equilibrium adsorbing capacity(qe)increased with the rise of temperature.When the initial concentration of MB was 80mg/L,of all the hydrogels,hydrogel HOA gained the maximum qe,the value was 20.09 mg/g.The qe of hydrogels increased with the extension of time,but adsorbing rate become slow.The qe of hydrogels decreased with the rise of temperature,and decreased sharply at the temperature of LCST.Increasing of pH would lead the raising of qe,and the absorbing would reach its equilibrium when pH was 7.0.