Chain end-group selectivity using an organometallic Al(iii)/K(i) ring-opening copolymerization catalyst delivers high molar mass,monodisperse polyesters |
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Authors: | Wilfred T Diment Charlotte K Williams |
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Institution: | Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Road, Oxford OX1 3TA UK, |
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Abstract: | Polyesters are important plastics, elastomers and fibres; efficient and selective polymerizations making predictable, high molar mass polymers are required. Here, a new type of catalyst for the ring-opening polymerization (ROCOP) of epoxides and anhydrides combines unusually high chain end-group selectivity, fast rates, and good molar mass control. The organometallic heterodinuclear Al(iii)/K(i) complex, applied with a diol, is tolerant to a range of epoxides/phthalic anhydride and produces only α,ω-hydroxyl telechelic polyesters with molar masses from 6–91 kg mol−1, in all cases with monomodal distributions. As proof of its potential, high molar mass poly(vinyl cyclohexene oxide-alt-phthalic anhydride) (91 kg mol−1) shows 5× greater flexural strain at break (εb = 3.7%) and 9× higher maximum flexural stress (σf = 72.3 MPa) than the previously accessed medium molar mass samples (24 kg mol−1). It is also enchains phthalic anhydride, vinyl cyclohexene oxide and ε-decalactone, via switchable catalysis, to make high molar mass triblock polyesters (81 kg mol−1, Đ = 1.04). This selective catalyst should be used in the future to qualify the properties of these ROCOP polyesters and to tune (multi)block polymer structures.A heterodinuclear Al(iii)/K(i) organometallic ring-opening copolymerization catalyst shows exceptional rates, end-group selectivity and good loading tolerance to deliver monodisperse polyesters with molar masses up to 91 kg mol−1. |
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