Study On Properties Of Solutions And Hydrogels Of Sulfobetaine Polymer

Betaine polymer is one of the typical zwitterionic polymers,and its unique antipolyelectroylte properties are shown to be of potential application in the areas of drug release,anti-protein adsorption,antithrombotic materials and other fields.Among them,poly(sulfobetaine methacrylate)(poly SBMA)is particularly attractive for the basic researches and practical applications due to its easy synthesizing and good stability.There have been a large number of reports on the properties of betaine polymer solutions since the 1960 s to the 1990 s,in recent years,most of the reports have focused on the properties of the modified betaine copolymer solutions,and the properties of the homopolybestaine is less reported.Therefore,the thorough understanding of the solution properties of polyzwitterion can provide the basis knowledge guidance for designing such polyzwitterion copolymer to extend its application in biomedicine and other fields.In this paper,we take poly(3-[Dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]azaniumyl]propane-1-sulfonate))(poly SBMA)as the research object to investigate the effects of the concentration of Na Cl and temperature on the molecular size of the poly SBMA in detail.It was found that poly SBMA molecular size grows continually and eventually approaches to an asymptotic value with the increase of the concentration of Na Cl(c Na Cl),which can be expressed by a continuous function.Previous studies had showed that the molecular size of the poly SBMA decreased with the increase of temperature for the poly SBMA dissolved in a high concentration of Na Cl aqueous solution(2.0 mol/L).However,the relationship between the temperature and the molecular size of poly SBMA at low c Na Cl has not been reported up to now,while in this paper,it showed that the swelling behavior of poly SBMA at low c Na Cl was quite different from it at high c Na Cl and the molecular size increased linearly with the increase of temperature.It has been reported that the single molecular chain of poly SBMA in dilute solution tends to collapse into a globule conformation through theoretical analysis and molecular simulation methods.In this paper,the single molecular chain of poly SBMA was directly observed via AFM test,which showed that the single chain of poly SBMA on the substrate at dry state appears to be a spherical segment,and the apparent size of the dried chain is basically the same as it is in solution.It mean that the internal structure still remains from solution state to dried state after it was landed on the substrate.This finding contributes to a deeper understanding of the molecular chain packing situation in solid surface modified poly SBMA membranes.The inter-or intra-chains association behaviors of poly SBMA indued another important property of its solution——phase separation.In this paper,the effects of the temperature and the molecular weight on the phase behaviors of the poly SBMA in various concentrations of Na Cl aqueous solutions at the critical transparent state were studied via UV-vis analytical techniques.The results showed that the concentration of poly SBMA critical structural units required to reach the critical transparent state increased with the increase of the concentration of Na Cl solution,and the number of Na Cl needed(RC)in per mole of structure unit of poly SBMA in the critical state decreased.This indicates that there is a positive polymer concentration effect in the transparency transition of the poly SBMA solution at the critical state,that is,the higher the concentration of poly SBMA structural units,the more transparent the solution.The higher the molecular weight of poly SBMA or the lower the solution temperature,the faster the RC reduction rate,the more remarkable the poly SBMA polymer concentration effect.A fitting formula about the viscosity average molecular weight of poly SBMA can be obtained from fitting the linear relationship between RC and the double logarithm of the critical polymer concentration,which provided a new method for viscosity average molecular weight measurement.In view of the above research that there existed a positive polymer concentration effect on the critical transparency transition of the dilute solution of poly SBMA,in this paper,the phase behaviors of poly SBMA as-prepared concentrated solutions were further studied.Various concentrations of poly SBMA as-prepared concentrated solutions(10wt% ~ 37.5wt%)were synthesized via free radical solution polymerization,and the phase transitions of poly SBMA as-prepared solutions from transparent to opaque were studied via UV-vis analytical techniques.The results showed that the phase transition temperature(TT)decreased with the increase of poly SBMA concentration(cpoly SBMA),which stood in contrast to the phase behavior of the most usual water-soluble polymer reported in the literature.Therefore,in this paper,the factors affecting the TT of poly SBMA were discussed in detail.The results showed that the poly SBMA concentration exerted the most important impact on the transition temperature,but the effect of the molecular weight and its distribution was very little.And it was found that the equilibrium concentration of poly SBMA solution(c*poly SBMA)was very high(40.1wt%),which led to the poly SBMA as-prepared solutions(10.0wt%<cpoly SBMA<37.5wt%)studied in this work were at over-swelling states.In view of this special phenomenon,combined with thermodynamic equilibrium theory,in this paper,a reasonable explanation for the above abnormal phase behavior of poly SBMA solution was given.In addition,as the swelling behavior of poly SBMA as-prepared solution could be controlled by the chemical crosslinking agent,the effect of the chemical crosslinking agent on the phase behavior of poly SBMA as-prepared solution was also studied.The result showed that the higher the crosslink ing agent content,the lower the phase transition temperature,which further confirming the above conclusions.According to the antipolyelectroylte properties of the poly SBMA solution,a chemical crosslinking hydrogel of poly SBMA with salt sensitivity was successfully synthesized by adding a small amount of crosslinking agent(BIS),and its swelling and deswelling behaviors in water or Na Cl solutions were studied in detail.The results showed that the swelling degree of the gel in water was much lower than that in Na Cl solution;The process of the swelling behavior followed Schott second-order diffusion kinetics,the initial deswelling rate,the gel deswelling rate and the release quantity of water of the gel at deswelling equilibrium were all decreased with the increase of the polymer concentration.Then we further investigated the release behavior of theophylline in poly SBMA gel.The results showed that the release behavior of theophylline in poly SBMA gel follows the non-Fickian diffusion model.As the mechanical properties of poly SBMA were very poor,which limited its the application in the biomedical or other fields.Therefore,a zwitterionic hydrophobic association hydrogel(SB-HA-gel)based on the biocompatible zwitterionic monomer SBMA which used as the main hydrophilic monomer,dimethylaminoethyl methacrylate bromotetradecane(DM-HB)that with antibacterial properties was used as the hydrophobic monomer and the surfactant sodium dodecyl sulfate(SDS)was synthesized through the micellar copolymerization.The effects of SBMA,DM-HB and SDS on the tensile properties of SB-HA-gels were studied.And the SB-HA-gels with high tensile mechanical properties were obtained by adjusting the ratio between the components.In addition,the results of the swelling measurements of SB-HA-gels at high temperature and high salt concentration showed that it has good high temperature resistance and high salt resistance,which improved the poor properties of the usual physical crosslinking hydrogels in high temperature and high salt concentration,and this is expected to be applied in the field of biomedical devices or other field.In summary,in this paper,the sulfobetaine polymer(poly SBMA)was used as the research object to study its dilute solution properties,its phase transition behavior at high concentration,its chemical crosslinking gel swelling behavior and the mechanical properties of its hydrophobic associative hydrogel.The results enriched the bas ic theory of zwitterionic polymers and expanded the potential application of zwitterionic polymer hydrogels in biomedicine and other fields.