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Studied On Preparation And Properties Of Conjugated Microporous Near-infrared Photothermal Conversion Polymers

Posted on:2022-09-28Degree:MasterType:Thesis
Country:ChinaCandidate:M J WuFull Text:PDF
GTID:2481306476498584Subject:Chemical Engineering
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Near-infrared(NIR)light can deeply penetrate living tissue.Photothermal therapy of cancer utilizes NIR photothermal conversion materials to transform the absorbed NIR light into thermal energy and raise local temperature,and then to achieve the kill of cancer cells.Therefore,the development of high efficient NIR photothermal conversion materials has attracted an increasing attention.However,for so-far developed conjugated polymer(CP)-based NIR photothermal conversion materials,most are linear type and suffering from the low photothermal conversion efficiency.Considering porous materials with high specific surface area and abundant pore structure generally have capability to reflect and scatter light hierarchically and thus enhance its absorption,this thesis work proposes to transform linear NIR conjugated polymers into porous materials by copolymerization with a third monomer bearing multiple functionalities for improving their thermal performance.The work chose diketopyrrolopyrrole(DPP)polymers,which have excellent NIR-absorbed abilities,and a four-functionalized tetraphenylethylene(TPE),a special building block for aggregation-induced emission materials,as studying polymers and third monomer,respectively.Two series conjugated microporous DPP polymers with different side chains were designed and synthesized by varying the feeding ratio of TPE monomer.The influences of TPE integration and its content on polymer structure,NIR absorption,and photothermal conversion properties were investigated in detail.Their basic influencing principle and basic structure-property relationship were correlated and discussed.The detail work can be divided into the following two parts:In the first part of the work,a series polymers named PEHDPPT-x TPE(x = 0.167,0.25,0.5)were prepared by two-step Stille copolymerization of a dibrominated DPP monomer with 2-ethylhexyl side chain(EHDPP),a bistrimethylstannylated thiophene monomer,and a four-brominated TPE monomer,in which the feeding ratio of TPE monomer(x)was adjusted to be 0.167,0.25,and 0.5,as referred to thiophene monomer.So that,in the polymers,the content of TPE,the length of linear chain segment between two adjacent TPE moieties,and the size of pore structure were varied accordingly.Studies found that as TPE content increases,the specific surface area increases,and photothermal conversion efficiency also gradually enhanced.The reference polymer(PEHDPPT)without TPE integration displayed a photothermal conversion efficiency(?)of 12.0%,while TPE-introduced polymers showed ? values of 19.7%(PEHDPPT-0.167TPE),23.2%(PEHDPPT-0.25TPE)and 25.1%(PEHDPPT-0.5TPE).In the second part,by considering their possible biomedical applications,polymer side chains were changed into hydrophilic 2-[2-(2-methoxethoxy)ethoxy]ethyl(Teg)and a new series polymers,PTeg DPPT-x TPE(x=0.167,0.25,0.5),were synthesized.Compared with PEHDPPT-x TPE,the new polymers,PTeg DPPT-x TPE,showed a wider light-absorption spectrum extending into NIR-II region with a 100-150 nm red-shifted onset,a narrower optical band gap down to 1.13-1.24 e V.Moreover,they have a larger solubility in polar solvents like DMF,and a better photothermal conversion performance.The measured photothermal conversion efficiencies are 34.1% for PTeg DPPT-0.167 TPE,29.4% for PTeg DPPT-0.25 TPE,and 28.8% for PTeg DPPT-0.5TPE,which are enhanced by a factor of 73%,26%,and 15%,respectively,as compared to those of PEHDPPT-x TPE.Meanwhile the maximum steady-state temperature was observed to increase 10?18 ?.These results indicate that Teg modification is favor for NIR light absorption and photothermal conversion.However,PTeg DPPT-0.5TPE series,the photothermal conversion efficiency slightly dropped with the increment of TPE content.This may be because the structure of TPE is strongly hydrophobic and not a NIR absorption moiety.The increase of its content will reduce the polymer solubility and NIR absorption,and thus affect photothermal conversion efficiency.In summary,the work demonstrates the basic properties and photothermal conversion performance of linear NIR conjugated polymers can be modulated by transforming linear structure into microporous ones by copolymering a third monomer having multiple functionalities.Whether the performance is improved or not and the degree of improvement is closely related to the structure of the starting polymer,the third monomer and its integrating content,which needs to be fully considered in the design.
Keywords/Search Tags:Porous Conjugated Polymers, Near Infrared Absorption Materials, Photothermal Conversion, Diketopyrrolopyrrole, Tetraphenylethylene
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