Fluorescencespectraofladderlikepolyphenylsilsesquioxane(LPPS)andladderlike1,4-phenylene-bridgedpolyvinylsiloxane(LPPVS)havebeenmeasuredasafunctionoftemperature(4-55℃),indilutetetrahydrofuransolution.Theexcimer(IE)tomonomer(IM)intensityratio(IE/IM)ofLPPSdilutesolutionshowsadoublelinearArrheniusplotwithabreakpointascribabletoatransitiontemperatureTr.Thisbehaviorhasnotbeenfoundforsinglechainpolyorganosiloxanes.WhenIn/EofLPPSwasplottedagainst1/T,italsogaveadoublelinearplotwithonebreakpoint,whichwasfoundinsinglechainpolyorganosiloxanes.ThedifferentbehaviorsbetweenLPPSandsinglechainpolyorganosiloxanesmaybemainlyattributedtotherelativelyrigiddouble-chainmacromolecularbackboneofLPPS.However,theln(IE/IM)ofdiluteLPPVSsolutionversus1/Tshowsasimplelinearvariationwithapositiveslopewhichconfirmsourproposition.ThedifferencebetweenthefluorescenceresultsofLPPSandthoseofLPPVSmaypossiblyderivefromtheirstructuredifferencesandcooperativemotioninbackbonechainbonds.
