Therefore, the focus of this dissertation is to first characterize these fundamental properties for various conjugated polymers, and then uncover their correlations with the chemical structure in order to ultimately predict the mechanical performance of stretchable electronics.The glass transition temperatures (Tg) for regioregular (RR) and regiorandom (RRa) poly(3-hexylthiophene-2,5-diyl) (P3HT) and poly-((9,9-dioctylfluorene)-2,7-diyl-alt-[4,7-bis(thiophen-5-yl)-2,1,3-benzothiadiazole]-2’,2”-diyl) (PFTBT) are unambiguously determined by linear shear oscillatory rheology.This method then allows systematic investigation of the effects of molecular weight and side chain regioregularity of P3HT on Tg.Tags: Essay On The Love Song Of J Alfred PrufrockEnglish 102 Research Paper TopicsCustom Research Paper WritingAmerican Revolution Essay QuestionsResearch Papers In Mechanical EngineeringLeet Speak EssayGcse Level English Questions CourseworkBusiness Plan For Bakery ShopRules Used In Writing Literary And Formal EssaysStory And Critical Essay On Her First Ball By Mansfield
Kinetic analysis and modeling explains the accelerated fluorescence switching observed in the system, producing new insights that will both contribute to more structural understanding of similar systems and lead to potential applications that harness similar effects.
As the molecular weight of pure RR P3HT decreases, the possibility of forming tie chains in RR P3HT decreases, eventually leading to isolated crystal domains and viscoelastic liquid behavior at long times.
By adding more RRa P3HT to the blends, the mass crystallinity determined by differential scanning calorimetry decreases from 0.58 to nearly zero, and the intercrystalline distance increases drastically from 10 to 40 nm based on the small-angle X-ray scattering.
This semi-empirical correlation requires only one adjustable parameter on the relative difference in atomic mobility between a conjugated and a non-conjugated atom and predicts the Tg ± 25 °C with 95% confidence for nearly all conjugated polymers with alkyl side chains.
Other attempts of correlating Tg with side chain mass fraction and packing length are also illustrated but deemed as unsatisfactory because of the limited applicability in only certain groups of conjugated polymers.
The molecular weight dependence of backbone Tg is modeled by the Flory-Fox equation, yielding Tg = 22 °C, 6 °C and 144 °C in the long chain limit for RR P3HT, RRa P3HT and PFTBT, respectively.
Furthermore, for RR P3HT, a different molecular weight dependence of Tg is seen below Mn = 14 kg/mol, suggesting this is the typical molecular weight of intercrystalline tie chains, based on our hypothesis that RR P3HT has 16 K higher Tg than RRa P3HT due to stretched tie chains.