Photoreaction and Molecular Reorientation in a Nanoscaled Film of Poly(methyl 4-(methacryloyloxy)cinnamate) Studied by Two-Dimensional FTIR and UV Correlation Spectroscopy

Abstract

Photoreaction and photoinduced molecular reorientations in nanoscaled films of poly(methyl 4-(methacryloyloxy)cinnamate) (PMMCi) were investigated through two-dimensional (2D) correlation analyses of their infrared (IR) and ultraviolet (UV) absorption spectra. In the PMMCi film the presence of three distinct chromophore types was evident: isolated trans-isomeric cinnamoyl moieties and parallel and end-to-end cinnamoyl aggregates. Their photoinduced reorientations take place in the following sequence: isolated trans isomeric chromophores f parallel chromophore aggregates f end-to-end chromophore aggregates. It turns out that they react photochemically at different rates. The PMMCi polymer molecules were found to undergo both photoisomerization and photodimerization upon UV irradiation, with the trans-cis isomerization of the isolated trans isomeric cinnamoyl moieties occurring more rapidly than the photodimerization of the cinnamoyl aggregates. Of the photodimerization processes, the reorientation of the parallel cinnamoyl aggregates precedes that of the end-to-end cinnamoyl aggregates. The isolated chromophores may partly involve in the photodimerization, but its fraction is expected small because of the film in a confined geometry. The cinnamoyl moiety was found to be present as two rotational conformers, trans-s-trans and trans-s-cis conformers. Upon UV irradiation, the trans-s-trans conformer changes before the trans-s-cis conformer. The cinnamoyl moieties undergo a cooperative reorientation with the methacryloyloxy units during photoreaction. The photoinduced molecular reorientations occur in the following sequence: trans isomer f phenyl ring f trans-s-trans conformer f trans-s-cis conformer f photodimer.

Polycinnamates and Block Co-polymers Prepared by Atom Transfer Radical Polymerization and Microwave Irradiation

“…On the other hand, is important to note that the described above photoprocess can be also monitored by FT-IR spectroscopy. Figure 4 shows the FT-IR spectrum of the PCEMA-2 film irradiated with UV light for varying time of irradiation, where the main absorption bands can be regarded in analogy to similar observations discussed earlier [40]. In particular, the absorption band at 1717 cm −1 corresponding to the conjugated C=O stretching vibration of the cinnamate group is overlapped with that of the C=O stretching vibration in the methacryloyloxy function, whereas the absorption bands at 1637 and 979 cm −1 are ascribed to the vinylene C=C stretching vibration, and the transvinylene C-H deformation in the cinnamate group, respectively.…”

High performance polyimides for applications in microelectronics and flat panel displays

“…The search for new methods that do not suffer from the shortcomings of the rubbing process has led to the development of several approaches to polymer alignment layer surface treatment based on irradiation of the polymer with linearly polarized ultraviolet light (LPUVL). 41,48,49,[74][75][76][77][78][79][80][81][82][192][193][194][195][196][197][198][199][200][201][202][203][204][205][206][207][208][209][210] These techniques have attracted considerable attention in academia and industry because they offer the possibility of rubbing-free production of LC aligning films.…”

Photopatternable Conducting Polymer Nanocomposite with Incorporated Gold Nanoparticles for Use in Organic Field Effect Transistors

“…It is supposed to be caused by the UV-induced degradation of the CI molecules after the saturation of its photoreaction on the AuNP surface. 36,41 It shows that we can obtain the reasonable electrical mobilities and UV-controllable FET properties of P3HT-AuNPs-CI film from 0 to 5 min-treatment of UV light. The changes in molecular orientation upon UV irradiation were examined by UV/vis spectroscopy of P3HT and P3HT-AuNPs-CI films, as shown in Figure 7.…”

“…The vibrational bands in the spectrum could be assigned in accordance with results reported previously. 35,36 The intensities of the band at 1634 cm −1 and 975 cm −1 (due to the vinylene C=C stretching vibration and the trans vinylene C-H deformation vibration in the cinnamoyl chromophore, respectively) decrease as the UV exposure time increases. In particular, we can observe the peak shift of the C=O stretching vibration from 1709 to 1724 cm −1 with increasing exposure.…”