Coupling Reaction of Two Kinds of Molecular-Weight Controlled Biodegradable Polymers

Abstract

ABSTRACT:Poly(ε-caprolactone) (PCL) having controlled molecular weight was synthesized by ring opening polymerization of ε-caprolactone (CL) initiated by ethanol with stannous(II) octanoate or scandium(III) trifluoromethane sulfonate as a catalyst. The hydroxyl end group of the resulting polymer was converted to trimethylsiloxyl group by using hexamethyldisilazane. On the other hand, poly(vinyloxy-t-butyldimethylsilane) (PVOTBDMS) was obtained by aldoltype of group transfer polymerization. Under the presence of ZnBr 2 or TiCl 4 as the catalyst, the coupling reaction of above two precursor polymers was carried out so as to build PCL-block-PVOTBDMS with controlled molecular weight and narrow molecular weight distribution. The PCL-block-PVA as the final goal could be obtained by elimination of the silyl groups in the above block copolymer.KEY WORDS Biodegradable Copolymer / Block Copolymer / Aldol-GTP / Poly(vinyloxy-tbutyldimethylsilane) / Poly(ε-caprolactone) / Living Ring-Opening Polymerization / In recent years, biodegradable polymers have attracted more and more attention from many fields to replace the traditional polymers owing to the increasing environmental problems caused by polymer disposal after use. It has been reported that they can be efficiently degraded into non-toxic water-soluble oligomers by a great number of living cells or microorganisms widely inhabited in the natural environment, then the water-soluble oligomers can be reutilized in many ways and finally changed into water, carbon dioxide or methane through several metabolic procedures of microorganisms. [1][2][3][4][5] It is well known that aliphatic polyesters are the most promising class of biodegradable materials which can be prepared by biosynthesis and chemical process 6-8 such as polycondensation and ring-opening polymerization.Poly(ε-caprolactone) (PCL) is one of the wellstudied aliphatic polyesters, which can be easily synthesized by CL with ethanol as an initiator and stannous(II) octanoate (Sn(Oct) 2 ) as a catalyst. 9-11 Up to present, Sn(Oct) 2 and aluminum triisopropoxide (Al(Oi-Pr) 3 ) have been most conventional catalysts for the ring-opening polymerization of lactones. 10, 12 Recently Kobayashi et al. insisted that rare earth metal triflates such as Sc(OTf) 3 can be used as an intriguing Lewis acid catalyst in organic synthesis. 13 Successful ring-opening polymerization (ROP) of CL using Sc(OTf) 3 was firstly reported by Nomura et al., showing the formation of PCL with very narrow molecular distribution even at 25

Novel Biodegradable Copolyesters Containing Blocks of Poly(3‐hydroxyoctanoate) and Poly(ε‐caprolactone): Synthesis and Characterization

“…The hydroxyl end group was converted into a trimethylsiloxyl group by using hexamethyldisilazane. [21] Hexamethyldisilazane was used to mask the hydroxyl group at the terminal of the PHO chain. In the 1 H NMR spectrum shown in Figure 5, the terminal methylene proton (CH 2 OH) signal at 4.0 ppm decreased with the passage of time and a new methylene signal at 4.1 ppm, assignable to CHOSi(CH 3 ) 3 , appeared, indicating that the hydroxyl end group of PHO can easily react.…”

A novel initiating system for ring‐opening polymerization of ε‐caprolactone: Synthesis of triarm star‐shaped poly(ε‐caprolactone)

“…[22][23][24] Known from other common catalysts, the activity of metal triflates would not be restrained by moisture and air. Moller et al, 25 Zhou et al, 26 and Nomura et al 27,28 reported the ROP of CL using scandium triflate [Sc(OTf) 3 ] as catalyst preparing LPCLs with controlled molar mass and very narrow molar mass distribution at room temperature. However, there is no reference concerning the preparation of SPCLs with metal triflates.…”

Amphiphilic Poly(ε-caprolactone)–Poly(vinyl alcohol) Block Copolymer: Preparation from a Bifunctional Initiator

“…10 In our previous work, 11 we have succeeded in synthesis of Poly("-caprolactone)-blockPoly{vinyloxy(tert-butyl)dimethylsilaneg, (PCL-b-PVOTBDMS), through a coupling method. Each block unit could be prepared by ring-opening polymerization (ROP) of CL and aldol-type group-transfer polymerization (Aldol-GTP) of VOTBDMS, respectively.…”