Experimental Study On The Crystallization Behavior And Glass Transition Behavior Of Polymer Chains On CNTs

CNTs have wide application prospects in many fields due to their excellent physical and mechanical properties.CNT array and CNT sponge provide nanoscale confined space and have a significant influence on the crystalline behavior and glass transition behavior of polymer/CNT composites.Polymer/CNT nanocomposites have been widely studied in recent years.In our work,a MWCNT array was grown by a thermal chemical vapor deposition method.P(VDF-TrFE)/CNTA composites were prepared by immersing CNT arrays in a P(VDF-TrFE)solution and drying them.In the presence of CNTs,the molecular chains and ?-phase crystal of P(VDF-TrFE)are oriented,and the ferroelectric property is improved.In addition,we also use CNT arrays to study the glass-transition behavior of PMMA chains in intertube channels of carbon nanotube arrays.Glass-transition behavior of PMMA/CNTA nanocomposite is strongly influenced by the structures of the the nanocomposite or orientation of CNTs in the nanocomposite.In the presence of CNTs,the relatively mobile polymer at the free surface of PMMA coating on CNTs can lead to a decrease in Tg,while the low-mobility polymer in the interfacial zone near CNT sidewalls exhibits slow dynamics,which is related to an increase in Tg.Therefore,the PMMA chains with reduced mobility in the interfacial zone might give arise to a Tg increase of the PMMA/CNTA nanocomposite compared to bulk PMMA.We also studied the glass-transition behavior of polymer(PMMA or PS)films on CNT sidewalls of carbon nanotube sponges and graphene oxide sheet.For polymer thin films coated on the CNT sidewalls,the value and sign of Tg deviation were mainly determined by competition between the free surface effect and the interfacial interactions.Therefore,we tuned the polymer-substrate interactions by coating CNT walls with amphiphilic SDS molecules.The effects of free surface layer and interfacial interaction between substrates and polymer films on the glass transition behavior of polymer films were studied.When the polymer-substrate interactions are strong,the Tgs of polymer films are close to bulk Tg value.When the interfacial interactions are weak,the mobile liquidlike free surface layer dominates the glass transition behaviors of thin polymer films.