Preparation And Characterization Of Biomass-based Branched Polymers

The feedstock used for preparation of synthetic resin, chemical fibre, rubber and otherpolymer materials is shifting from petroleum resource to renewable resources such as woodcellulose, starch, non edible oils and fats, etc, by various technical approach, which eventuallyexpect to achieve an effective replacementof petroleum based products. Currently, the mainpurpose of the research on renewable biomass based polymer materials is to obtain a novel"green" polymers whose physical and chemical properties is similar or better than those ofpetroleum based similar polymers by concise design and synthesis strategy. In this paper, thebackbones of cellulose, castor oil or other renewable resources used as starting material, weregrafted by petroleum based monomers like hydroxyethyl methacrylate (2-HEMA), as well asby renewable monomers such as rosin based monomers and oil based monomers by atomtransfer radical polymerization (ATRP), respectively, in order to obtain cellulose basedpolymer with brush structure, and castor oil based polymer with star shaped (three arms)structure. FT-IR,1H-NMR, solubility, GPC, TEM, TGA, AFM, mechanical property test etc,were then used to characterize the structure and initiating activity of cellulose or castor oilbased initiators and as well as counterpart polymers.The relationship of the structure ofcopolymer composition and thermodynamic, dynamics, etc, were also discussed. Theseresearchs will provide a good theoretical basis for the design synthesis and application of novelbiomass based polymers by using the renewable resources as a feedstock.1. By using LiCl/dimethyl amine solvent system, cellulose based macroinitiators used forthe ATRP were prepared. In this case, a macroinitiators with bromide content (initiating point)of4.17nmol/g, which can dissolve in DMF, THF and others solventss, was synthesized withfeeding molar ratio of cellulose unit and2-bromo isobutyryl bromine feeding of1:5, and usedto prepare the cellulose-g-poly(2-hydroxyethyl methacrylate)(Cell-g-PHEMA) applyingCuBr/Pentamethyldiethylenetriamine (PMDETA) as catalytic system. By controlling the molarratio of monomer, initiator, catalyst and ligand, as well as the reaction temperature rangingfrom40℃to60℃, poly(2-HEMA) was grafted on the cellulose backbone by ATRPpolymerization. The radius of hydration spherical micelles of prepared polymer was about80nm. The TGA analysis showed that the thermal stability of cellulose initiator andCell-g-PHEMA polymer and decreased, while compared raw material cellulose. 2. By using the CuBr/PMDETA catalyst system and controlling the molar ratio ofmonomer, initiator, catalyst and ligand, two kinds of resin acid monomers（DAEMA、DAEA）with different structures wereapplied to conduct the "graft from" ATRP on the cellulosebackbone. Varying the monomer feed ratio could lead to the polymers with different molecularweight. In the kinetics curve of Cell-g-PDAEMA（or PDAEA）graft polymer, the linearrelation of ln([M]0/[M]) with the timeshowed that polymerization was basically controllable,and the polymerization activity of DAEMA was higher than that of DAEA. The glass transitiontemperature of the graft copolymer Cell-g-PDAEMA（or PDAEA）was83.2℃（PDAEA，51.8℃）. It was found that hydrophobic properties, as well asUV absorption properties of theresulting cellulose polymers increased after the introduction of resin monomers. TheTGAanalysis indicated that the thermal stability of the resin acid monomer graft cellulosepolymers were obviously higher than that of cellulose.3. Two series of brush graft copolymers cellulose-g-poly (n-butyl acrylate-co-dehydroabietic acid ethyl methacrylate)(Cell-g-P (BA-co-DAEMA)) and biological basis ofcellulose-g-poly (methacrylic acid ethyl Laurate alcohol ester-co-dehydroabietic acid methylacrylic acid)(Cell-g-P (LMA-co-DAEMA)) were synthesizedby “grafting from” atom transferradicalpolymerization (ATRP). By manipulating the molar ratios in the P(BA-co-DAEMA)andP(LMA-co-DAEMA) side chains, graft copolymers with varying glass transition temperatures（-60-50℃) were obtained.. Tensile stress-strain and creep testing showed that the graftcopolymers had good mechanical properties. When the molar ratio of monomer and initiatorwas1000:1, the yield stress of the grafted polymer samples was0~2.5MPa, and the maximumof Young’s modulus was99MPa. All graft copolymers showed elastic strain recovery valuesbetween50%and85%, and manifested remarkable elasticity at strain deformation (500%ormore) beforeexperiencing failure, which were indicative of rubber-like elasticity. AFM andSAXS analysis confirmed that copolymers had no phase separation and wasdisordered.Meanwhile,all copolymers also showed a good hydrophobicity and thermal stability.4. Castor oil based ATRP initiator was prepared by the fast and efficientesterificationreaction between2-bromoisobutyryl bromideandhydroxyl group in castor oil. The structure ofthe initiator was then confirmed by FT-IR,1H-NMR, and13C-NMR. Sequently, theinfluencing factors on ATRP graft polymerization of castor oil were investigated. In these cases,poly(methyl methacrylate)(PMMA) was used to graft castor oil by ATRP. It was found that thecatalytic effect of copper bromide was better than that of CuCl, and when the dosage of copperbromide was low, ATRP polymerization process achieve a good control. The amount of solvent percentage which was at more than70%could make the polymerization of ATRP runsmoothly.Additionally, the use of high polar solvent could be helpful to polymerization.5. Based on the previous work, castor oil based star shape (three arms) copolymers withunique structure were synthesized by "graft from " ATRP of methyl methacrylate (MMA) andbutyl acrylate (BA). These polymerizations were indicative of well-controlled. TGA analysisshowed that the onset decomposition and maximum decomposition occurred in the temperatureranging from350oC to450oC. By varying the molar ratio of MMA and BuA, the copolymerswith different glass transition temperature were obtained. The mechanical analysis showed thatthe optimum usage of MMA was ranging from40%to60%. When the content of MMA was50%, the copolymer showed a elongation of approximate300%and a maximum stress. Inaddition, when the content of MMA increased, the fracture strain decreased and fracture stressincreased.