Preparation And Properties Of Bottle-brush Polymers And Collagen Based SIPN Gels

Bottle-brush polymers are highly branched macromolecules and possess uniqueproperties due to its special molecular structure. Proteoglycans-natural bottle-brush polymersexist in the extracellular matrix of cartilage and airway mucus abundantly. The shockabsorption and lubrication properties of cartilage and the mucociliary clearance of lungairways are controlled by bottle-brush proteoglycans, which inspires the design and synthesisof polymers with similar architectures. This thesis was based on the macromolecular structureof cartilage proteoglycan to carry out the study. In this paper, chitosan（CHIT）, polyethyleneglycol monomethyl ether（mPEG）, and2-acrylamide-2-methyl propane sulfonic acid （AMPS）were selected as the base material because of their good biocompatibility. Two kinds ofbottle-brush polymers were prepared using host-guest self-assembly and free radicalcopolymerization. And the two kinds of bottle-brush polymers/collagen gel were preparedwith semi-interpenetrating network structure.Firstly, The host polymer（β-CD-CHIT） was synthesized via aldehyde aminecondensation reaction between β-cyclodextrin monoaldehyde and–NH2of chitosan chain.The guest polymer（ADA-mPEG） was prepared by esterification reaction that the adamantylgroup was introduced into the molecular chains of polyethylene glycol monomethyl ether. Theself-assembly between the host polymer and the guest polymer happened through the specicalinclusion complexation between β-cyclodextrin with adamantane in the solution to form abottle-brush hydrophilic macromolecules-polyethylene glycol chain as side chain andchitosan as main chain. FTIR spectroscopy and1H NMR spectroscopy were used tocharacterize the structure of the host polymer, the guest polymer and assembly material.Based on the above research, UV-vis spectra were employed to observe theself-assembly process and record the real-time change of the spectrum of mixed solution inthe assembly process. The size distribution of the particles in the solution was determinedusing Malvern Zetaszier Nano-ZS. The effect of assembling time, temperature, the addition ofcompetition molecule on self-assembly were studied through the change of the diameter ofthe particles in solution. The results showed that the size distribution would change a lotbefore and after assembly. And over a certain time range, the size distribution of particles in the solution remain basically stable. The increasing of temperature and the addition ofcompetition molecule had an important impact on the structure of supramolecular assemblies.Microcrystalline quartz was also used to study the assembly process.The results showed thatthe dissipation increases suddenly became quicker at one point, which mean that theconformation on the surface of membrance changed resulting from the host-guest assembly.The morphology of the particles of supramolecular assemblies on silicon wafer surface wasobserved using atomic force microscope in the wet state.The results showed that the particlesin the solution was circular with a diameter size of about300nm consistent with themeasurement of Malvern Zetaszier Nano-ZS.In the fourth chapter, aqueous free radical polymerization was employed to synthesizethe bottle-brush copolymer P （mPEG-AC-co-AMPS） using potassium persulfate as theinitiator. The structure of of the macromonomer and copolymers was confirmed by FTIR and1HNMR spectrum. Gel permeation chromatography was used to investigate the effect ofinitiator concentration and monomer ratio on the molecular weight of the copolymer. Theconductivity titration method was used to measure the sulfonate ion content in copolymeraccording to the principle of the formation of polyelectrolyte-surfactant composite.The effectof the monomer ratio and initiator concentration on the sulfonate ion content in copolyme wasanalysed in detail. The thermal properties of the copolymer was explored through DSC. Theresults indicated that the homopolymer of two reactive monomer does not exist in copolymerand when mPEG component in copolymer increased, glass transition temperature woulddicrease.Finally, two kinds of collagen-based semi-interpenetrating gel were prepared using EDC/NHS as crosslinking agent: collagen/P （mPEG AC-co-NaAMPS） and collagen/assembliesgel. The swelling property of collagen/P（mPEG AC-co-NaAMPS） gel in water wasstudied.The results indicated that the gel possessed excellent swelling property and reachedequilibrium at30min. The pH-sensitivity of SIPN gel was also explored by measuring theswelling ratio at different pH.It was displayed that the prepared collagen-based SIPN gelpossessed obvious pH sensitivity resulting from-NH2,-COOH and SO₃^-in gel. Scanningelectron microscopy was used to observe the surface morphology of SIPN gel samples,showing that two kinds of gels had significant channel structure.