Study On The Mechanical Properties Regulation Of Conjugated Polymers By Chlorinated Polyolefins

With the emergence of the new global energy revolution,organic solar cells have gained considerable attention as a green energy technology due to their light weight,flexibility,low cost,and the ability for large-area solution processing.Flexible organic solar cells,in particular,have the added advantage of being bendable and attachable to surfaces of various shapes,making them promising power supply modules for future wearable electronic devices.The key component of flexible organic solar cells is the core active layer comprised of conjugated polymers.Although conjugated molecules possess a certain degree of mechanical flexibility,their rigid structure leads to poor mechanical properties.This property makes it difficult to meet the requirements of highstrain applications that are necessary for future flexible and wearable electronic devices.Therefore,it is necessary to improve the mechanical properties of conjugated polymers through appropriate regulation strategies,such as chemical modification,physical blending,etc.However,chemical modification strategies suffer from issues such as complex synthesis,high cost,and significant batch-to-batch variability.Physical blending,on the other hand,faces challenges regarding compatibility and limited applicability.In summary,it is necessary to develop a simple,efficient,and universally applicable strategy for tuning the mechanical properties.This study proposes a novel strategy that involves the non-covalent physical crosslinking of conjugated polymers through the introduction of chlorinated polyolefins.This strategy effectively enhances the mechanical properties of the conjugated polymers while preserving their efficient optoelectronic performance.The specific research findings are as follows:1.Propose a new strategy for regulating the mechanical properties of conjugated polymers based on "physical cross-linking".The physical crosslinking system is constructed by polyvinyl chloride(PVC)and conjugated polymers.Therefore,the mechanical properties of conjugated polymers could be effectively regulated.This study found that after introducing 5 wt% PVC into PM6,the specific viscosity of the solution increased significantly from 1.96 m Pa?s to 4.87 m Pa?s,and the crack-onset strain of film increased significantly from 10.12% to 19.35%.Combining Fourier Transform Infrared Spectroscopy(FTIR)and X-Ray Photoelectron Spectroscopy(XPS)techniques,we proved that there is a non-covalent interaction between PM6 and PVC,thus forming a physical cross-linking network and effectively improving the mechanical properties of PM6.In addition,PVC additives have a minor impact on the efficiency of photoactive layer of PM6-based organic solar cells(only decreased from 17.53% to 16.96%).Conjugated polymers with excellent mechanical properties and optoelectronic properties were obtained using this novel mechanical regulation strategy.2.This study investigates the influence of varying chlorine content on the mechanical properties and rheological behavior of conjugated polymers by selecting three chlorinated polyolefins with different chlorine content but similar molecular weight and distribution: chlorinated polyethylene(CPE),PVC,and chlorinated polyvinyl chloride(CPVC)(in the order of increasing chlorine content: CPE < PVC < CPVC).This study revealed that adding 5 wt%CPE resulted in a remarkable reduction in both the elastic modulus and tensile strength of conjugated polymers,while solution viscosity remained unaffected.On the other hand,the impact of introducing 5 wt% CPVC on the mechanical properties and solution viscosity of conjugated polymers could be neglected.Through the employment of FTIR and XPS spectroscopy,it was determined that the CPE blend system does not possess any non-covalent interaction,whereas the non-covalent interaction strength in the PVC blend system is significantly greater than that in the CPVC blend system.Further research has demonstrated that the non-covalent interaction is characterized by a local conformational nature,wherein the isotactic component of the PVC molecule exhibits a predominant tendency to partake in non-covalent interaction formation.CPE and CPVC prepared by random chlorination have fewer stereoregular regions,while PVC prepared by polymerization reaction contains more stereoregular regions,which can form higher density physical crosslinking with conjugated polymers,thereby significantly improving the solution viscosity and film mechanical properties of conjugated polymers.