No abstract

A long-standing challenge in polymer chemistry has been to prepare synthetic polymers with not only well-defined molecular weight, but also precisely controlled microstructure in terms of the distribution of monomeric units along the chain. Here we describe a simple and scalable method that enables the synthesis of sequence-controlled multiblock copolymers with precisely defined high-order structures, covering a wide range of functional groups. We develop a one-pot, multistep sequential polymerization process with yields 499%, giving access to a wide range of such multifunctional multiblock copolymers. To illustrate the enormous potential of this approach, we describe the synthesis of a dodecablock copolymer, a functional hexablock copolymer and an icosablock (20 blocks) copolymer, which represents the largest number of blocks seen to date, all of very narrow molecular weight distribution for such complex structures. We believe this approach paves the way to the design and synthesis of a new generation of synthetic polymers.

We describe an optimized method to prepare multiblock copolymers. The approach is based on our previously reported use of reversible addition–fragmentation chain transfer (RAFT) polymerization, which here has been optimized into a fast, versatile, efficient, and scalable process. The one-pot, multistep sequential polymerization proceeds in water, to quantitative yields (>99%) for each monomer addition, thus circumventing requirements for intermediate purification, in 2 h of polymerization per block. The optimization of the process is initially demonstrated via the synthesis of a model decablock homopolymer (10 blocks) of 4-acryloylmorpholine with an average degree of polymerization of 10 for each block ( Đ = 1.15 and livingness >93% for the final polymer). Both the potential and the limitations of this approach are illustrated by the synthesis of more complex high-order multiblock copolymers: a dodecablock copolymer (12 blocks with 4 different acrylamide monomers) with an average degree of polymerization of 10 for each block and two higher molecular weight pentablock copolymers (5 blocks with 3 different acrylamide monomers) with an average degree of polymerization of 100 per block.

This review deals with two of the most commonly used methods for the preparation of amines: the reductive amination of aldehydes and ketones and the hydrogenation of nitriles. There is a great similarity between these two methods, since both have the imine as intermediate. However, due to the high reactivity of this intermediate, primary, secondary and/or tertiary amines are obtained (often simultaneously). The relation of the selectivity to different substrate structures and reaction conditions is briefly summarised, the main focus being on the catalyst as it is the most significant factor that governs the selectivity. Different mechanisms are discussed with the view to correlate the structure of the catalyst and, more particularly, the nature of the metal and the support with selectivity. The crucial point is the presumed location of the condensation and hydrogenation steps.

We report the synthesis by the reversible addition− fragmentation chain transfer process of well-defined decablock polymers with a final dispersity as low as 1.15 and a fraction of living chain as high as 97% after 10 successful block extensions, each taken to >99% monomer conversion. By using model decablock homopolymers of poly(N,Ndimethylacrylamide) and poly(4-acryloylmorpholine) of relatively low DP (10 units per block in average), we describe the theoretical and experimental considerations required to access high-order multiblock copolymers with excellent control over molecular weight distributions and high livingness.