Computer Simulation And Synthesis Of Amphiphilic Comb Like Polymer Superplasticizers

Amphiphilic comb like polymer superplasticizers, also known as comb likepolycarboxylate superplasticizers, is another revolutionary innovation following thenaphthalene superplasticizers. It has not only solved the problem that the naphthaleneand melamine superplasticizers have a excessive slump loss under low water andcement ratio, but also has a more excellent slump retention than the previoussuperplasticizers, so it earned widespread concern by the concrete scientificcommunity and industry. Because its water reducing and dispersion mechanism cannot be explained by the potential dispersion mechanism applied to naphthalenesuperplasticizers, and there is no unified conclusion until now. Using experimentalmethods to get its mechanism is under explore. Monte carlo simulation is a methodthrough collecting samples objectively and randomly to investigate the generalcharacteristics, and in the case of enough information and large enough samples, itcan objectively reflect the overall characteristics. With monte carlo computersimulation and the approaching ture energy between amphiphilic comb like polymerand cement particle, we can get the adsorption relationship between these two. Addingvisibile CAD drawing technology, we can visually observe the adsorption process andstate of amphiphilic comb like polymer adsorbing on the cement particle, as well aswhat kind of structure and molecular weight would have good adsorption, and this is avery good guide for superplasticizers synthesis.This thesis generally includes four parts:The first part describes the structural characteristics, synthesis as well asdomestic and foreign research progress of amphiphilic polymer and comb likepolymer, and then briefly describes the monte carlo simulation technology and itsapplication in polymer science community. List some scholars’ innovative achievement with monte carlo simulation in the field of polymer. Finally, introducethe amphiphilic comb like superplasticizers’ domestic and foreign research with theperspective of industrialization and related problems exist today.In the second part, we simulated the process of PAA/PEO copolymer adsorbingon the surface of cement particle with monte carlo simulation, and objectively showsthe molecular state and chain conformation of the amphiphilic comb like polymer inthe adsorption process. By studying different types of amphiphilic comb likepolymer’s adsorption distribution data on the surface of cement particle we discussedimpact of the structure, molecular weight and Polyoxyethylene ether side chain lengthon the adsorption. The results show that PAA/PEO copolymer in the adsorptionsimulation exist in the form of directly adsorbed polymer, indirectly adsorbed polymer,and free polymer. Directly and indirect adsorbed polymer can play water reducing anddispersion effect, and free polymer can not achieve water reducing and dispersioneffect. The carboxylic acid groups on the PAA/PEO copolymer molecules make thecomb like polymer adsorb on the surface of the cement particle rely on electrostaticadsorption, and Polyoxyethylene ether long side chains radially extending with thecement particle as its center to prevent the cement particles flocculation and collisionmainly to steric hindrance, thus play water reducing and dispersion effect. By meansof analyzing the monte carlo adsorption simulation data of different molecular weightand different side chain length PAA/PEO copolymers, we can obtained that thePAA/PEO copolymer with a polymerization degree more than6and polyoxyethyleneether side chain length more than8will play well water reducing and dispersioneffect.The third part based on the monte carlo simulation results. We used (meth) allylpolyoxyethylene ether, maleic anhydride, acrylic acid,2-propylene acrylamide-2-methyl-propanesultone as monomers and synthesized a kind of amphiphilic combpolymer contained sulfonic acid groups by means of molecular design. Its structurewas characterized by FTIR and HNMR, and its Molecular weight and molecularweight distribution were confirmed by aqueous gel chromatography. The resultsshowed that the amphiphilic comb like polymers contained sulfonic acid groups, carboxylic acid groups, and poly (ethylene oxide) ether long side chains weresynthesized, and they had a molecular weight of13,000or so, further more they had anarrow molecular weight distribution.We studied the effect of four monomers addition amount, the polyoxyethyleneether side chain length, the amount of superplasticizer admixture, maleic anhydridetype monomer species as well as adaptability between amphiphilic comb likesuperplasticizers and different brands cement on the superplasticizer performance andcompared the performance of the synthesized amphiphilic comb like polymersuperplasticizers with domestic and foreign products. The results showed that theoptimal ratio of four monomers was nAPEG (TPEG): nMA: nAA: nAMPS=1:2.3:2:1.5, and the best side chain length was25. the synthesized amphiphilic comblike polymer superplasticizers have advantages of low dosage, high water reductionrate and high cement particles dispersion, and have a good adaptability with threebrands of commonly used cement in the northeastern region. This kind ofsuperplasticizers has a quite performance with foreign products and a slightly betterperformance than domestic products.