Synthesis Of Poly(styrene-methacrylate) And Comparitive Studies On The Products As Pseudostationary Phases In Electrokinetic Chromatography

The self-assembled amphiphilic copolymer aggregates pseudostationary phase(PSP) can provide diverse selectivity for capillary electrokinetic chromatography(MEKC), because the composition and type of the amphiphilic copolymers are adjustable. My research group had been studied physicochemical properties and EKC performances of poly(methyl methacrylate-co- methacrylate)(P(MMA-co-MAA)). In the thesis, styrene as the hydrophobic monomer, possession of weaker polarity than MMA and conjugated π bond, amphiphilic random copolymer poly(styrene-co- methacrylic acid)(P(St-co-MAA)) has been synthesized. The physicochemical properties including the critical micelle concentration(CMC), polarity, surface charge density, hydrodynamic diameter and kinematic viscosity were investigated. The methylene group selectivity evaluated with five n-alkylphenone homologous series, the time window and linear solvation energy relationships(LSER) analysis were used to characterize the MEKC retention behavior and the selectivity. Basen on the previous work, all of these were compared with P(MMA-co-MAA) system. The amphiphilic block copolymer poly styrene-b- poly methacrylic acid(PSt-b-PMAA) was also synthesized, its physicochemical properties and EKC performance were mesusured and compared with those of P(St-co-MAA). This thesis mainly included the three parts.1. Five kinds of amphiphilic random copolymers P(St-co-MAA) with differerant monomer ratio were synthesized by radical polymerization, using styrene(St) and methyl methacrylate(MAA) as monomers. P(St-co-MAA) with five kinds of monomer ratio were all characterized by means of infrared spectroscopy(IF), nuclear magnetic resonance(NMR) and gel permeation chromatography(GPC). The results showed that P(St-co-MAA) can be successfully synthesized by this method. Five monomer molar feed ratio(St: MAA) is 0.43:1.00, 0.67:1.00, 1.00:1.00, 1.50:1.00, 2.33:1.00, respectively. The actual ratio(St:MAA) calculated by 1H-NMR is 0.53:1.00, 0.81:1.00, 1.16:1.00, 1.52:1.00, 2.37:1.00, respectively. The actual molar ratio is similar to the feed molar ratio. The number-average molecular weights(Mn) of five products are from 54,000 to 70,000. The weight average molecular weights(Mw) were from 63,000 to 83000, polydispersity was less than 1.20 respectively.2. Characterized the morphology of P(St-co-MAA) self-assembled aggregates by transmission electron microscopy, the results testified the formation of the aggregates. Their physicochemical properties and MEKC performance were investigated as well in the present work. The critical micelle concentration(CMC), polarity, surface charge density, hydrodynamic diameter and kinematic viscosity were used to characterize the solution physicochemical properties, while the methylene group selectivity evaluated with five n-alkylphenone homologous series, the time window and linear solvation energy relationships(LSER) analysis were used to characterize the MEKC retention behavior and the selectivity. All of these were compared with P(MMA-co-MAA) with the molar ratio of 7:3 and sodium dodecyl sulfate(SDS) micellar systems. The results showed that P(St-co-MAA) system(molar ratio of 7:3) had the minimum CMC and hydrodynamic diameter, the widest time window, the best methylene group selectivity and strong retention of both non-hydrogen bonding(NHB) and hydrogen bond acceptor(HBA) solutes, but this system has the minimum column efficiency. LSER analysis results showed that the cavity formation was the most important interaction between solutes and PSPs, and the hydrogen-bonding acidity was the second significant influence on selectivity and MEKC retention behavior. P(St-co-MAA) system with the molar ratio of 7:3 had the highest effect parameters in LSER. Compared the molar ratio 6:4 with 7:3 of P(St-co-MAA), the increase of the ratio of the hydrophobic group in the copolymer is favorable to selectivity. In comparison of P(St-co-MAA) and P(MMA-co-MAA)(monomer molar ratio both are 7:3), the decrease of the polarity of hydrophobic monomer is favorable to selectivity for hydrophobic solutes.3. Amphiphilic block copolymers PSt-b-PMAA was synthesized by atom transfer radical polymerization, the product was characterized by means of IF, NMR and GPC. The CMC, polarity, surface charge density, hydrodynamic diameter and kinematic viscosity were measured to characterize the physicochemical properties of PSt-b-PMAA solution, while the methylene group selectivity evaluated with five n-alkylphenone homologous series, the time window were used to characterize the MEKC retention behavior and the selectivity. The physicochemical prepertity and EKC characteristic were pcompared between P(St-b-MAA) and P(St-co-MAA) with the molar ratio of 6:4 systems. TEM showed that PSt-b-PMAA can form spherical micelle. The structre was more regular and the monodispersity was better than that of P(St-co-MAA). The actual ratio(St:MAA) calculated by 1H-NMR is 2.20:6.48. The type of copolymers impacts physicochemical properties and EKC significantly. Block copolymers is conducive to widen the time window, but lower column efficiency owing to slow mass transfer between PSP and the running buffer.