Preparation And Absorption Ability Studies Of Thermo Responsive PVCL Based Composites

Thermo-sensitive polymer undergoes reversible chemical,physical and conformational changes in response to external temperature stimulus.Its effective controlled polymerization method,surface grafting and assembly of nanostructures or morphologies have attracted considerable attention since 1990 s.Polyvinyl caprolactam(PVCL)is a popular thermosensitive polymer.It has favorable biocompatibility.The lower critical solution temperature could be tuned by controlling the polymerization degree.Therefore it exhibits potential applications in biomedicine field.In this study,poly vinyl caprolactam(PVCL)was selected as the object.The controlled polymerization and the surface initiated controlled polymerization of PVCL were studied.PVCL based nanofibers,microgels and inorganic/ organic core-shell structures were fabricated.The adsorption and elution properties of different PVCL nanostructures toward lysozyme were studied.Microgel with high adsorption abitity for membrane protein was engineered and utilized to functionalize Zn O quantum dot.The composite quantum dot was applied for labeling E.Coli.In the study of controlled polymerization of PVCL,Benzyl sulfanyl thio carbonyl sulfanyl propionic acid(BPA)was synthesized according to literature and used as chain transfer reagent.The reaction technique for Reversible Addition-Fragmentation Chain Transfer Polymerization(RAFT)was studied.To fabricate high specific surface area nanostructures in a quick and efficient way,electrospinning was applied to process the polymer.To improve the stablitiy of fibrous morphology,the PVCL was modified with methacrylate.Results indicate that BPA could narrow down the PDI of PVCL from 2.85 to 1.37.When MMA content was 10%,the fiber could swell below VPTT and maintain the fiberous morphology.The optimal parameters for electrospinning of PVCL-co-PMMA(10 % MMA)fiber are 11 k V Volt with electric field strength of 50 k V/m and concentration of 0.4 g/m L.The prepared PVCL-co-PMMA(10 % MMA)fibers adsorbed 1.18 mg/g lysozyme at 15 ?and could adsorbe 1.55 mg/g at 35 ?.In order to improve the adsorbing ability of PVCL based microgel for Lysozyme,and to better understand the contribution of each complementary functional group of amino acid.PVCL was assembled into microgels and modified with Tert butyl acrylamide(t BAM)and Acrylic acid(AAc).The influence of t BAM and AAc on the volume phase transition temperature(VPTT)and the adsorption capacity were investigated.Results indicated that t BAM content lowered the VPTT of microgel;the influence of AAc on VPTT was related to the content: 5 % AAc(n/n,feed ratio)lowered the VPTT of microgels and 10 % AAc increased the VPTT.Microgel with optimized composition captured 5.97 mg/g Lysozyme in p H 7 35 mmol/L phosphate buffer(p H 7)among which 2.41 mg/g was contributed by electrostatic force,3.56 mg/g was contributed by hydrophobic interaction.And 88.6% of the hydrophobic interaction contributed adsorption could be released at 2 °C.Surface initiated controlled polymerization was carried out on Titanium dioxide(Ti O2),an inorganic material that could be used as affinity adsortption ligand for phosphopeptide.Copper cation(Cu2+)frequently used for protein metal chelate affinity binding was selected for adsorbe measurement of the obtained Ti O2-PVCL.Ti O2 was modified with chain transfer agent BPA and O-ethyl-S-(1-methoxy)ethyl two thio carbonate(OEMED)respectively to initialize the surface polymerization of PVCL.Results indicated BPA modified Ti O2 successfully initiated the polymerization PVCL from the surface while PVCL was not detectable on surface of Rhodixan A1 modified Ti O2.When the feed ratio of Ti O2-BPA / monomer was 1.0/9.23(W/W),the grafting degree was 10.8 % with Mn 4000 of PVCL.When feed ratio of Ti O2-BPA/monomer was 1.0/27.8(W/W),the grafting degree was 45.5 % with Mn 10 000 of PVCL.The adsorption of Lysozyme on Ti O2–PVCL was 15.0 mg/g.In order to facilitate the separation of PVCL after elution,PVCL was grafted from Fe3O4@Si O2 core-shell particles.The influence of processing parameters on morphology of the particles was discussed.Results indicated that when the concentration of Fe3O4 suspension was 0.015 mg/m L and the concentration of TEOS was 0.023 g/m L,spherical and uniform Fe3O4@Si O2 core-shell particles was obtained.The core-shell particle can tolerate 1 mol/L HCl and 0.01 mol/L Na OH solutions.When the surface grafting degree of PVCL on Fe3O4@Si O2 was 46.6 %,the temperature controlled reversible binding capacity for Lysozyme was 1.34 mg/g.Microgel with high adsorbing ability to membrane protein was engineered and utilized to functionalize the fluorescence Znic Oxide(Zn O)quantum dot with targeting ability.The influence of each content on adsorbing ability to membrane protein of E.Coli was discussed.Water stable thermo responsive Zn O quantum dot was fabricated and used for labeling E.Coli.Results indicated that positive component of the microgel is the main factor that affected the adsorption of E.Coli.In the range of 0-40 %,the higher the content of hydrophobic functional groups was,the stronger the adsorption ability of the microgels to E.coli was.The adsorbe ability of the microgel was very sensitive to the change of positively charged monomer content when the content is 0~10%;and is not sensitive to the change when positively charged content is more than 10%.The emission wavelength of the obtained Zn O/PNIPAM composite microgel could be tuned by changing the addition amount of KOH solution.The emission wavelength of QDs synthesized in 1.0 m L 0.5 mol/L KOH was 441 nm.After a storage time for 15 days,the quantum yield of QD3 decreased by 11.3%.The emission wavelength was unchanged.The obtained Zn O/PNIPAM(QD3)exhibited binding ability to E.Coli.