Study On The Molecular Morphology Of Several Water-soluble Polymers By Laser Light Scattering

The molecular morphology of poly merhas the complex and change fulcharacteristicsin solution.In this research work,linear polyethlene glycol?PEG?,self-made Polyacrylic acid?PAA?,self-made PEG-PAA polymer?polycarboxylate,PCE?and Pluronic block polymers havebeen studied in solution by dynamic light scattering?DLS?,explored theinfluence ofsolution properties and hydrodynamic radius?R_h?of polymer under the condition of concentration,temperature,pH,electrolyte.The main results are as follows:?1?When the concentrationwas 2.00 g/L,the R_h of PEG molecular weightof 4000,10000,20000 were 2.30nm,3.45nm,4.90nm.PEG withhigh molecular weight has thelarger R_h.As the pH raiesd from 2 to 12,the R_h of PEG with different molecular wight were increased 10%,the molecular morphology didn't change sighificantly.The kinetic energy of PEG increased with the rise oftemperature,R_h of PEG with different molecular wight were decreased 30%.The particle sizesof PEG were controllable under different temperatures.The R_h and surface tensionof PEG were decreasedunderelectrolyteofCaCl₂andNaCl,whichrepresented colligativeproperties.Methanol,ethanol and ethylene glycolsignificantly reducedthe R_hof PEG molecular,furthermore,methanol hadgreater impact on PEG withlarger molecular weight,PEG with smaller molecular weight obviously responded to ethylene glycol.?2?Firstly,three kinds of linear PAA molecules were synthesized.When the concentration was 2.00 g/L,the R_h of PAA molecular weight of 4300,13400,26900were 2.93nm,4.25nm,5.32nm.PAA withhigh molecular weight hadthe larger R_h.The R_h of PAA increased with the rise of pH,alkaline conditions could promote ionization of carboxylic groupsin PAA solution,the R_h of PEG with different molecular wight were increased 3⁴ times,the molecular chains were more extended.Similarlytheincreaseoftemperature,slowing increased the R_hvalue of PAA,which appeared as a peak value,the R_hof PEG with different molecular wight also increased 1.5 times.Over the peak temperature,the molecular chain contracted,system finally retured to relative equilibrium state.The addition of electrolyte?like CaCl₂,Na₂SO₄,NaCl?caused the decreasingthe R_h value of PAA molecule.Since Ca²⁺could coordinate with the carboxyl groups in the PAA molecule,the PAA moleculeswere affected by Na₂SO₄obviously,PAAmolecules inCaCl₂solution wereprior to reach a“steady state”.?3?The influence on the PCE molecular morphologywith different interfering factorswas studied.The results showed that the addition of PCE molecules could significantly change the surface tension of the aqueous solution.When the concentration was 2.00 g/L,the R_h of three proportioning PCE were 8.70nm,9.90nm,11.40nm.The smaller theside chain density was,the bigger the R_h.When pH<7,the surface tension and R_h almost remained unchanged.Whereas when pH>7,the alkali couldsignificantlypromote ionization of PCE polymer,causing a stretch in the molecular chain.The R_h of PCE with the smallest side chain density increased most obviously,from 11.40nm to 13.95nm.The molecular morphology of PCE was mainly influenced by the main chain PAA with the increase of temperature.The PCE molecule with higher anionic charge density obviously responsedto CaCl₂,compared to NaCl solution,R_h increased from 11.40nm to 15.59nm.?4?The results showed that the critical micelle concentration?cmc?ofP123and F127were 0.05 g/L and 2.50 g/L at room temperature.The R_h and surface tension of P123and F127 almost remained unchangedin acid environment.With the enhancedalkalinity in the solution environment,the R_h of F127 increased significantly compared with P123,R_h increased from 11.20nm to 12.65nm,whereasthe surface tension of the two samples all decreased slowly.The increase in temperaturewas helpful to reduce the critical micelle concentration of P123 and F127,and formed a stable micelle whichwith larger particle size.The R_h of P123increased from 14.50nm to 26.93nm,The R_h of F127increased from 11.20nm to 17.60nm.In the wake of adding three electrolytes,the R_h of P123 and F127 increased,and effect of Na₂SO₄was more obviously.Due to the closely properties of hydrophilic and hydrophobic in butyl alcohol,butyl alcohol had very special expansion effect in P123and F127 solutions,whichwas different from the other three kinds of organics.