Synthesis Of Sequence-controlled Polymers Research Articles

Sequence-controlled proline-based polyacrylamides via RAFT polymerization: Influence of sequence structure on polymers performances

The synthesis of sequence-controlled polymers is an important emerging trend in recent polymer science. However, the relationship between the sequence structure and performance of the polymer was rarely studied. Here, we synthesized a series of sequence-controlled proline-based multi-block copolymers via one-pot iterative RAFT polymerization, it achieved high monomer conversions (>98%), precise control of molecular weight, and low polydispersity. The relationship studied between the sequence structure of multi-block copolymers and thermoresponsive performance revealed that the LCSTs of these copolymers are sequence dependent, and it can be altered by variation the sequence structure. In addition, temperature-variable 1H NMR analysis and dissipative particle dynamics (DPD) simulation technique were chosen to further study on the nature of phase transition and the relationship between sequence structure and thermoresponsiveness. Thus, we have demonstrated a concise method to construct sequence-controlled bio-based copolymers with precisely adjustable structures and functions which can be applied to the design of biological and medical materials.

Synthesis of sequence-controlled polymers via sequential multicomponent reactions and interconvertible hybrid copolymerizations

Synthesizing artificial polymers with precise sequence structures, such as their biological analogues, is a serious challenge and of great importance in polymer science. Recently, step-growth polymerization and chain growth polymerization have been the main synthesis methods for preparing artificial sequence-regulated polymers. However, it is difficult to obtain sequence-controlled polymers with sufficient molecular diversity via step-growth polymerization; on the other hand, chain-growth polymerization generally requires laborious repetitive monomer feeding. In this focus review, the sequential multicomponent reactions for preparing periodic sequence-controlled polymers with sufficient molecular diversity and complexity and the interconvertible hybrid copolymerizations producing hybrid multiblock copolymers rapidly in one pot are highlighted. We have developed sequential multicomponent reaction and interconvertible hybrid copolymerization methods to prepare sequence-controlled polymers. The sequential multicomponent reaction combines more than two different multicomponent reactions in one pot to prepare periodic sequence˗controlled polymers with sufficient molecular diversity. The interconvertible hybrid copolymerization method uses trithiocarbonate compounds to combine radical polymerization of vinyl monomers and anionic ring-opening polymerization of thiirane monomers, resulting in hybrid multiblock sequence-regulated polymers.

Synthesis of sequence-controlled polymers with pendent “clickable” or hydrophilic groups via latent monomer strategy

Herein, we designed and synthesized functional maleimide containing “clickable” or hydrophilic functional groups that was used to synthesis advanced sequence-controlled functional polymers via latent monomer strategy. A number of sequence-controlled functional polymers were synthesized by changing the polymerization temperature and controlling the initial charge ratio with highly programmable controlled temperature. Finally, a preliminary study on the thermal properties of the obtained sequence-controlled polymer revealed that the content and the distribution of the hydrophilic monomer in the polymers have a profound effect on the properties of the polymers.

The effect of amine-functionalized 1,1-diphenylethylene (DPE) derivatives on end-capping reactions and the simulation of their precision for sequence control

Three amine-functionalized 1,1-diphenylethylene (DPE) derivatives (DPE-(NMe2)2, DPE-NMe2 and DPE-SiH/NMe2) were used to study the end-capping reactions of poly(styryl)lithium (PS-Li) for investigating the effect on end-capping of electron-donating groups in DPE structures. In situ1H NMR was used to measure the kinetic parameters of end-capping reactions. When the DPE derivative was held constant in the PS-Li capping reaction, the kinetic parameter (kSD) did not change with the variance of either concentration or degree of polymerization of PS-Li. Additionally, the kSD value changed dramatically when various electronic properties of the DPE derivative substituents were modified. Electron-withdrawing groups accelerated the end-capping reaction, while electron-donating groups decelerated it. The kSD experimental values of DPE-(NMe2)2, DPE-NMe2 and DPE-SiH/NMe2 were found to be 0.155 × 10−3, 1.26 × 10−3, and 6.24 × 10−3 L1/2 mol−1/2 s−1, respectively. An intuitive model was established to simulate the precision of the sequence-controlled copolymerization with DPE derivatives based on investigations of end-capping kinetics. The model depicts the degree of fictitious styrene propagation for the chain insertion of one DPE derivative unit. The fictitious degrees of polymerization of styrene (FDPs) for DPE-NMe2 and DPE-SiH/NMe2 were calculated to be 37 and 13, respectively, suggesting that using DPE derivatives containing an electron-withdrawing group in the synthesis of sequence-controlled polymers might lead to a more precise structure.

Synthesis of sequence-controlled polymers via sequential thiol-ene and amino-yne click reactions in one pot

Sequence-controlled polymers are prepared by the combination of thiol-ene click reaction and amino-yne click reaction. Due to the high selectivity of the amine unit and thiol unit toward thiolactone, methacrylate, propiolate, etc., the sequence of the resulting polymers can be easily controlled by monomer-addition sequence. Moreover, thiol-ene click reaction and amino-yne click reaction can be carried out under mild conditions without need of any catalyst. Different kinds of sequence-controlled copolymers have been prepared by the combination of thiol-ene click reaction and amino-yne click reaction in one pot. NMR spectra and GPC traces confirmed the formation of polymers with high molecular weight and controlled sequence structure. Therefore, we provide a new method for the preparation of functional polymers with well-controlled sequences.