Block copolymers form the basis of the most ubiquitous materials such as thermoplastic elastomers, bridge interphases in polymer blends, and are fundamental for the development of high-performance materials. The driving force to further advance these materials is the accessibility of block copolymers, which have a wide variety in composition, functional group content, and precision of their structure. To advance and broaden the application of block copolymers will depend on the nature of combined segmented blocks, guided through the combination of polymerization techniques to reach a high versatility in block copolymer architecture and function. This review provides the most comprehensive overview of techniques to prepare linear block copolymers and is intended to serve as a guideline on how polymerization techniques can work together to result in desired block combinations. As the review will give an account of the relevant procedures and access areas, the sections will include orthogonal approaches or sequentially combined polymerization techniques, which increases the synthetic options for these materials.

The copolymerization of tert-butyl glycidyl ether (tBuGE), allyl glycidyl ether (AGE), ethoxyethyl glycidyl ether (EEGE) and 1,2-epoxybutane (BO) with γ-thiobutyrolactone was investigated using benzyl alcohol–phosphazene bases as initiating systems. The prepared copolymers display perfect (poly­(ester-alt-sulfide)) alternating structures for all epoxide monomers as evidenced by 1H, 13C, and 2D NMR and MALDI–TOF mass spectrometry. A marked influence of the reaction temperature on the occurrence of transesterification side reactions has been evidenced. In particular, at elevated temperature, transesterification reactions led to the formation of alternating macrocycles. The choice of the phosphazene base (tBuP4, tBuP2, or tBuP1) has a strong impact on the system reactivity and on the control of the polymerization. The use of tBuP1 led to very slow polymerization rates. The polymerization is much faster in the presence of tBuP2 even at low temperature. The use of tBuP4 shows an intermediate polymerization rate and enabled a good polymerization control at moderate temperatures. Finally, the synthesis of well-defined polyether-block-poly­(ester-alt-sulfide) and the polymerization of a challenging substituted γ-thiolactone were proven to be feasible.

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This contribution fills the need for quantitative mechanistic and kinetic information for epoxide polymerizations catalyzed by tBuP4 phosphazene base.