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.

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.

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The synthesis of multiblock copolymers is often considered as synthetically challenging and time consuming. In this contribution, the development of a remarkably efficient and versatile procedure to access multiblock copolymers via reversible addition-fragmentation chain transfer (RAFT) polymerization is reported. The robustness and versatility of the RAFT process is demonstrated in this report by preparing multiblock copolymers using uncommon experimental conditions. The synthesis of each block was performed in the presence of air and only required 3 minutes to reach >98% monomer conversion. This approach removes the necessity to deoxygenate the solution and permits access to complex copolymer structures in very short time periods. For example, this process allowed the preparation of a heptablock homopolymer with a well-defined architecture in just 21 minutes. We also discuss the limitations inherent to this approach. This strategy is shown to be particularly efficient when blocks with low degrees of polymerization (DP < 20) are targeted. For blocks with higher DPs (DP > 50), the procedure is typically limited to the preparation of di-or triblock copolymers.Functional block copolymers are fascinating architectures with unique properties that render them particularly attractive for applications ranging from medicine, 1,2 materials, 3 energy 4 and nanotechnology. 5,6 The access to such synthetically demanding architectures was greatly facilitated with the advent of controlled/"living" radical polymerization techniques, also known as reversible deactivation radical polymerization (RDRP), 7 such as atom transfer radical polymerization (ATRP), 8,9 nitroxide-mediated radical polymerization (NMP), 10,11 reversible addition-fragmentation chain transfer (RAFT) 12-15 and macromolecular design via interchange of xanthates (MADIX) 16-18 polymerizations. These methods enable the production of well-defined polymeric materials with predetermined molar masses, narrow molar mass distributions, chainend functionality, and they can be coupled with efficient post-polymerization modification strategies (e.g. 'click' chemistry). [19][20][21][22][23][24][25] Despite the relative ease of preparing block copolymers (i.e., di-or triblock copolymers) via RDRP methods in comparison with, for example, ionic living polymerizations, the production of multiblock copolymers still remains a challenging and time consuming task. This is mainly due to the necessity to remove any unreacted monomer before the subsequent block is synthesized, 26-31 as the non-removal of monomer would lead to the synthesis of quasi-block copolymers. 32Additional issues include a decrease in chain-end fidelity with increasing the number of blocks.Recently, Cu(0)-mediated radical polymerization 33-38 and RAFT polymerization 39-44 have demonstrated great potential to produce well-defined, multiblock architectures, in particular by reaching full monomer conversion, thus avoiding tedious, intermediate purification steps.

Precise control over the location of monomers in a polymer chain has been described as the ‘Holy Grail' of polymer synthesis. Controlled chain growth polymerization techniques have brought this goal closer, allowing the preparation of multiblock copolymers with ordered sequences of functional monomers. Such structures have promising applications ranging from medicine to materials engineering. Here we show, however, that the statistical nature of chain growth polymerization places strong limits on the control that can be obtained. We demonstrate that monomer locations are distributed according to surprisingly simple laws related to the Poisson or beta distributions. The degree of control is quantified in terms of the yield of the desired structure and the standard deviation of the appropriate distribution, allowing comparison between different synthetic techniques. This analysis establishes experimental requirements for the design of polymeric chains with controlled sequence of functionalities, which balance precise control of structure with simplicity of synthesis.

The synthesis of high-order multiblock copolymers by one-pot sequential monomer addition RAFT polymerization is examined by use of modeling and simulations using PREDICI. The system is the previously experimentally investigated model multiblock homopolymer system comprising 10 blocks of N,Ndimethyl acrylamide with average degree of polymerization 10 for each block. The simulations show that despite 10 chain extensions to full conversion, the number of dead chains at the end of the process is only %7%. The number fraction of dead chains is known from the number of chains generated from the initiator, and the conditions can thus be tailored with regards to the livingness required.

Room temperature RAFT polymerisation for the design of multiblock acrylate/acrylamide copolymers.