Polyimide(PI)is widely used in high-frequency communication technology due to its exceptional comprehensive properties.However,traditional PI has a relatively elevated dielectric constant and dielectric loss.Herein,th...Polyimide(PI)is widely used in high-frequency communication technology due to its exceptional comprehensive properties.However,traditional PI has a relatively elevated dielectric constant and dielectric loss.Herein,the different cross-linked structures were introduced in PI matrix and conducted a detailed discussion on the influence of cross-linking agent content and cross-linking structure type on the overall performance of PI films.In comparison to the dielectric constant of 2.9 of neat PI,PI with an interchain cross-linking structure containing 2 wt%1,3,5-tris(4-aminophenyl)benzene(TAPB)(interchain-PI-2)exhibited the reduced dielectric constant of 2.55 at 1 MHz.The PI films with intrachain crosslinking structure containing 2 wt%TAPB(intrachain-PI-2)exhibited the lowest dielectric constant of 2.35 and the minimum dielectric loss of0.0075 at 1 MHz.It was due to the more entanglement junctions of intrachain-PI resulting in decreased carrier transport.The thermal expansion coefficients of both interchain-PI and intrachain-PI films were effectively reduced.Moreover,in contrast to interchain-PI films,the intrachain-PI films maintained colorlessness and transparency as the cross-linking agent content increased.This work compared the effects of two different cross-linked structures on the performance of PI films and provided a feasible way to obtain low-k PI films with excellent comprehensive performance for 5G applications.展开更多
Single-chain nanoparticles represent an emerging class of nanomaterials designed to mimic protein's folding paradigm.Intrachain covalent crosslinking toward the formation of single-chain nanoparticles encounters c...Single-chain nanoparticles represent an emerging class of nanomaterials designed to mimic protein's folding paradigm.Intrachain covalent crosslinking toward the formation of single-chain nanoparticles encounters complex energy landscapes,leading to the potential occurrence of misfolding issues.While noncovalent crosslinking can circumvent this issue,the resulting single-chain nanoparticles exhibit lower structural stability compared to their covalently crosslinked counterparts.In this study,we present a novel approach for the synthesis of single-chain nanoparticles,achieved through the combination of non-covalent and covalent intramolecular crosslinking.Cyanostilbenes grafted onto the linear polymer form intrachain non-covalent stacks aided by hydrogen bonds,leading to the formation of non-covalently crosslinked single-chain nanoparticles.These nanoparticles undergo conversion to covalently crosslinked nanostructures through subsequent photo-irradiation using[2+2]photocycloaddition,a process facilitated by the supramolecular confinement effect.Consequently,the resulting single-chain nanoparticles demonstrate both intrachain folding efficiency and substantial stability,offering significant potential for advancing applications across diverse fields.展开更多
The photo-physical characteristics of semiconductor polymer are systematically stud- ied through comparing poly （9,9-dioctylfluorene） （PFO） and poly （9,9-dioctylfluorene-co- benzothiadiazole） （F8BT）. The quant...The photo-physical characteristics of semiconductor polymer are systematically stud- ied through comparing poly （9,9-dioctylfluorene） （PFO） and poly （9,9-dioctylfluorene-co- benzothiadiazole） （F8BT）. The quantum chemical calculation shows that the introduction of benzothiadiazole unit facilitates the intrachain charge transfer （ICT） and modulates the electronic transition mechanism of polymer. The transient absorption measurement exhibits that intrachain exciton relaxation is dominant in the decay of excited PFO in a monodis- perse system and intrachain exciton interaction could appear at high excitation intensity. In F8BT solution, the ICT state exists and participates in the relaxation of excited state. The relaxation processes of PFO and F8BT in the condensed phase both accelerate and show obvious exciton-exciton annihilation behavior at high excitation intensity. At the same excitation intensity, the mean lifetime of F8BT is longer than that of PFO, which may be assigned to the excellent delocalization of charge.展开更多
The excited state photophysics of low bandgap polymer APFO3 has been investigated in detail. The chemical calculations confirm that the intrachain charge transfer （ICT） may occur after photo-excitation and is mainly...The excited state photophysics of low bandgap polymer APFO3 has been investigated in detail. The chemical calculations confirm that the intrachain charge transfer （ICT） may occur after photo-excitation and is mainly responsible for the first absorption band. The transient absorption results confirm that ICT indeed exists and competes with the vibra-tional relaxation at the same time, when APFO3 is in a monodisperse system. This ICT process would disappear due to the influence of interchain interaction when APFO3 is in the condensed phase, where the exciton decay would be dominant in the relaxation process after photoexcitation. The photoexcitation dynamics of APFO3 film blending with PC61BM are presented, which shows that the exciton may be dissociated completely as the percentage of PC61BM reaches ～50%. Meanwhile, the photovoltaic performance based on blend het-erojunction shows that the increase of photocurrent is little if the percentage of PC61BM exceeds ～50%. Overall, the present study has covered several fundamental processes taking place in the APFO3 polymer.展开更多
Since the discovery of doped polyacetylene over four decades ago,significant advances have been made in understanding charge transport and metallic behavior in linear conductive polymers[1].Traditional models emphasiz...Since the discovery of doped polyacetylene over four decades ago,significant advances have been made in understanding charge transport and metallic behavior in linear conductive polymers[1].Traditional models emphasize intrachain coupling within large conjugated systems,with charge transport occurring along the conjugated chain direction,while interchain hopping serves as a secondary conduction mechanism[2].展开更多
基金financially supported by the National Natural Science Foundation of China(No.52103029)。
文摘Polyimide(PI)is widely used in high-frequency communication technology due to its exceptional comprehensive properties.However,traditional PI has a relatively elevated dielectric constant and dielectric loss.Herein,the different cross-linked structures were introduced in PI matrix and conducted a detailed discussion on the influence of cross-linking agent content and cross-linking structure type on the overall performance of PI films.In comparison to the dielectric constant of 2.9 of neat PI,PI with an interchain cross-linking structure containing 2 wt%1,3,5-tris(4-aminophenyl)benzene(TAPB)(interchain-PI-2)exhibited the reduced dielectric constant of 2.55 at 1 MHz.The PI films with intrachain crosslinking structure containing 2 wt%TAPB(intrachain-PI-2)exhibited the lowest dielectric constant of 2.35 and the minimum dielectric loss of0.0075 at 1 MHz.It was due to the more entanglement junctions of intrachain-PI resulting in decreased carrier transport.The thermal expansion coefficients of both interchain-PI and intrachain-PI films were effectively reduced.Moreover,in contrast to interchain-PI films,the intrachain-PI films maintained colorlessness and transparency as the cross-linking agent content increased.This work compared the effects of two different cross-linked structures on the performance of PI films and provided a feasible way to obtain low-k PI films with excellent comprehensive performance for 5G applications.
基金supported by the National Natural Science Foundation of China(Nos.22371272 and 22301295)the Fundamental Research Funds for the Central Universities(Nos.YD2060002036 and WK5290000004)+1 种基金International Partnership Program of the Chinese Academy of Sciences(No.123GJHZ2022064MI)the Collaborative Innovation Program of Hefei Science Center,CAS(No.2022HSC-CIP014)。
文摘Single-chain nanoparticles represent an emerging class of nanomaterials designed to mimic protein's folding paradigm.Intrachain covalent crosslinking toward the formation of single-chain nanoparticles encounters complex energy landscapes,leading to the potential occurrence of misfolding issues.While noncovalent crosslinking can circumvent this issue,the resulting single-chain nanoparticles exhibit lower structural stability compared to their covalently crosslinked counterparts.In this study,we present a novel approach for the synthesis of single-chain nanoparticles,achieved through the combination of non-covalent and covalent intramolecular crosslinking.Cyanostilbenes grafted onto the linear polymer form intrachain non-covalent stacks aided by hydrogen bonds,leading to the formation of non-covalently crosslinked single-chain nanoparticles.These nanoparticles undergo conversion to covalently crosslinked nanostructures through subsequent photo-irradiation using[2+2]photocycloaddition,a process facilitated by the supramolecular confinement effect.Consequently,the resulting single-chain nanoparticles demonstrate both intrachain folding efficiency and substantial stability,offering significant potential for advancing applications across diverse fields.
文摘The photo-physical characteristics of semiconductor polymer are systematically stud- ied through comparing poly （9,9-dioctylfluorene） （PFO） and poly （9,9-dioctylfluorene-co- benzothiadiazole） （F8BT）. The quantum chemical calculation shows that the introduction of benzothiadiazole unit facilitates the intrachain charge transfer （ICT） and modulates the electronic transition mechanism of polymer. The transient absorption measurement exhibits that intrachain exciton relaxation is dominant in the decay of excited PFO in a monodis- perse system and intrachain exciton interaction could appear at high excitation intensity. In F8BT solution, the ICT state exists and participates in the relaxation of excited state. The relaxation processes of PFO and F8BT in the condensed phase both accelerate and show obvious exciton-exciton annihilation behavior at high excitation intensity. At the same excitation intensity, the mean lifetime of F8BT is longer than that of PFO, which may be assigned to the excellent delocalization of charge.
基金ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.21103161 and No.11274142） and the China Postdoctoral Science Foundation （No.2011M500927）.
文摘The excited state photophysics of low bandgap polymer APFO3 has been investigated in detail. The chemical calculations confirm that the intrachain charge transfer （ICT） may occur after photo-excitation and is mainly responsible for the first absorption band. The transient absorption results confirm that ICT indeed exists and competes with the vibra-tional relaxation at the same time, when APFO3 is in a monodisperse system. This ICT process would disappear due to the influence of interchain interaction when APFO3 is in the condensed phase, where the exciton decay would be dominant in the relaxation process after photoexcitation. The photoexcitation dynamics of APFO3 film blending with PC61BM are presented, which shows that the exciton may be dissociated completely as the percentage of PC61BM reaches ～50%. Meanwhile, the photovoltaic performance based on blend het-erojunction shows that the increase of photocurrent is little if the percentage of PC61BM exceeds ～50%. Overall, the present study has covered several fundamental processes taking place in the APFO3 polymer.
文摘Since the discovery of doped polyacetylene over four decades ago,significant advances have been made in understanding charge transport and metallic behavior in linear conductive polymers[1].Traditional models emphasize intrachain coupling within large conjugated systems,with charge transport occurring along the conjugated chain direction,while interchain hopping serves as a secondary conduction mechanism[2].
