Synthesis Of Hydroxylated Poly[Bis(2-Methoxyethoxy)Phosphazene] And Grafting Poly(e-Caprolactone)

Chapter 1It was introduced briefly that the current research and development ofbiodegradable polyphosphazenes, and summarization was given on thestructural characterization, mechanisms and effecting factors in degradation ofpolyesters and polyphosphazenes. The relevance and methods were stated tofunctionalize degradable polyesters and improve their hydorphilicity. Wesummarized the biomedical application of degradable polyphosphazenes inrecent years. The purpose of this thesis work was educed after discussed thatthe disadvantage of polyesters and advantage of polyphosphazenes.Chapter 2The reaction conditions of preparing the alcohol-functionalized poly[bis(methoxyalkoxy)phosphazenes] was identified by using PVME as modelpolymer to react with trimethylsilyl iodide. We investigated the influence ofreaction time, catalyst dosage and deprotection time on the final amount ofhydroxyl groups incorporated into PVME. The LCST of all polymers was determined, and LCST will rise via increase of the OH content in hydroxylPVME.Chapter 3Poly[bis (methoxyalkoxy)phosphazenes] was prepared by eitherTriethylamine-Process or Sodium-Alkoxide-Process. In comparison with theformer method, P-C1 can be substituted almost completely inSodium-Alkoxide-Process. Methylamine or aniline, Which was used to maskthe residual P-C1 in Triethylamine-Process, can react with Triethylamine tocreate ethylamine. We investigated the influence of reaction time on theviscosity of polyphosphazenes in Sodium-Alkoxide- Process, and the resultshows the viscosity will descend as reaction time extending.Methoxy end groups were cleaved from poly[bis(methoxyethoxy)phosphazenes by reaction with trimethlsilyl iodide to give silylated polymers,and then the silylated polymers were hydrolyzed to yield the alcohol-functionalized polymers. The correlation between the amount of ISi(CH₃)₃ andthe percentage of resultant alcohol functions was established, and thisfunctionalization reaction induced chain cleavage of the polymer as theamount of ISi(CH₃)₃ increased.Chapter 4Poly[bis(2-methoxyethoxy)phosphazene)-graft-poly(e-caprolactone) copolymers (PMEP-g-PCL) were prepared using Sn(â…¡)2-ethylhexanoate(SnOct₂) as catalyst and the hydroxyls in polyphosphazene as initiators. Thegrafting ratio and length of poly(e-caprolactone) side chains can be controlledvia changing the feeding dose of trimethylsilyl idide and e-caprolactone. Thestructure of PMEP-g-PCL copolymers were investigated by ¹H-NMR andinfrared spectroscopies. Thermal analysis demonstrated that PCL side chainsof PMEP-g-PCL possessed lower melting point and crystallinity than linearPCL with similar molecular weight. Higher raction temperature(140℃) causedchain scission of Poly[bis(2-methoxyethoxy)phosphazene). This material canbe applied in drug delivery in despite of lower molecular weight.Novel synthetic route, i.e. hydroxy coupling with carboxyl in thepresence of DCC and DMAP. PMEP-g-PCL copolymer was suggested to besynthesized successfully by infrared spectroscopies analysis.