Synthesis Of Advanced Gradient And Amphiphilic Sequence-Controlled Polymers

The precise sequence structure of biological macromolecules gives complexity and diversity of the nature.Inspired by nature,enormous efforts have been made to regulate the sequence of synthetic polymers within the last decades,which is expected to improve or endow novel properties/functions to the resulting polymers.The discovery of controlled radical polymerization?CRP?techniques has greatly promoted the development of polymer science,various methods for preparing sequence-controlled polymers have been reported.The research into the structure-property relationships and potential application of sequence-controlled polymers is no doubt one of the most challenging subjects in contemporary polymer science.This thesis is mainly about using latent-monomer strategy to synthesis sequence-controlled polymers.This strategy relies on the temperature-dependent retro Diels-Alder?rDA?reaction of the latent monomer.With programmable fluctuations of temperature,a variety of sequence-controlled polymers can be potentially fabricated.Herein,the latent-monomer-based strategy was further used to fabricate advanced gradient and amphiphilic sequence-controlled polymers.The specific research contents are as follows:?1?In this work,the comonomer pair of methyl methacrylate?MMA?and furan-protected propyl maleimide?FPMI?was judiciously selected to fabricate advanced gradient polymers via nonintrusive RAFT polymerization.Herein,the FPMI was used as the latent monomer,polymerizable PMI can be gradually released in situ via the rDA reaction of FPMI at 100 ??or above?to copolymerize with MMA in a gradient fashion due to intrinsic reactivity ratios.At low temperature,such as 40 ?,the rDA reaction for the release of maleimide could not be triggered.By deliberately manipulating the temperature of MMA CRP,polymerizable maleimide units can be incorporated into the“living”polymer chains at customized positions.Meanwhile,due to the intrinsic reactivity ratio of MMA?r₁>1?and PMI?0<r₂<1?,gradient sequences could be readily fabricated.Thus,diverse advanced gradient copolymers,including simultaneous,hierarchical,tri-blocky,and symmetrical gradient polymers,were easily prepared by changing the polymerization temperature and/or employing a bifunctional RAFT agent.Finally,the thermal properties of different advanced gradient copolymers with similar molecular weights and total PMI contents were explored.However,due to the low incorporation of PMI into the copolymer,the thermal properties of different advanced gradient copolymers were not significantly different.?2?In this section,a hydrophilic furan-protected maleimide?FHME?was designed and regarded as a latent monomer.At high temperature?either 100 ? or above?,FHME is deprotected by rDA reaction with the release of polymerizable maleimide units?HME?.Under low temperature?such as 40 ??,the rDA reaction does not proceed,meanwhile,FHME can not participate in polymerization.It is noted that the maleimide and styrene have a strong tendency to cross-propagation.Thus,in the course of CRP of styrene?St?together with the FHME at high temperature,the maleimide released in situ was immediately involved in cross-polymerization with St,created predictable sequence-controlled polymer chains and diverse sequences of St/HME amphiphilic copolymers were easily prepared.Through changing the initial feeding ratio of St/FHME,the contents of the HME units in polymer chains can be significantly tuned.The emulsifying properties and thermodynamic properties of the obtained amphiphilic copolymers were preliminary investigated.