New method for the synthesis of fully aliphatic telechelic α,ω-dihydroxy-polyisobutylene†
This paper reports a new method for the synthesis of α,ω-primary-dihydroxy PIBs (HO–PIB–OH) with a fully aliphatic backbone. Three aliphatic difunctional initiators with tertiary-methoxy, tertiary-chloride and tertiary-hydroxyl end groups (TMHDiOMe, TMHDiCl and TMHDiOH) were screened in conjunction with TiCl4 and DMA in a solution system (hexane–CH3Cl, 60/40, v/v). TMHDiOMe yielded only traces of PIB, while TMHDiOH and TMHDiCl yielded PIBs with a mixture of end group structures. The same initiators were also screened in heterogeneous systems (CH3Cl or CH2Cl2). TMHDiOMe/TiCl4 yielded no polymer in either diluent, CH3Cl, and TMHDiOH/TiCl4 led to olefinic end groups. While TMHDiCl/TiCl4 resulted in clean Cl–PIB–Cl in CH3Cl, the Ieff values were low and TMHDiCl was very unstable and difficult to isolate. Premixing TMHDiOH with TiCl4 in CH3Cl led to the in situ formation of TMHDiCl. Addition of hexane and IB, followed by end-capping with allyltrimethylsilane resulted in the formation of allyl–PIB–allyl. Click chemistry with HS–CH2–CH2–OH yielded α,ω-primary-dihydroxy-PIB (HO–PIB-OH) with Mn = 4085 g mol−1 and ĐM = 1.2. 1H-NMR analysis verified the structure of the HO–PIB–OH.