4BCMU-PDA

Fig. 23.29 The 7r-band region of the UPS spectra of 4BCMU-PDA on two different expanded scales. (From Ref. 107.)...

Figure 13 Optical absorption of the PDA poly-4BCMU in three differently ordered states (a) solution in chloroform (b) gel from toluene (dense homogeneous films cast from solution have similar, though slightly less structured, spectra) (c) single crystal.

The influence of chain conformation on mobility is clearly seen in the data for PDA-4BCMU. The mobility is highest for isolated, extended linear polymer chains produced at low concentration in the monomer crystal matrix and falls dramaticallyfor the disordered chains in a yellow solution, but is slightly... 

PDA-4BCMU Partially polymerised crystal Negative/Positive >2.7 xlO-4... 

PDA-4BCMU Yellow solution in dioxane Negative/Positive >7xl(T10... 

We have established an effective and simple method for preparing a variety of organic microcrystals in water. The solid-state polymerization of 4BCMU microcrystals was estimated to proceed from one end to the other end. The possibility of preparing PDAs with controlled molecular weight was qualitatively demonstrated. In the case of microcrystals of 14-8ADA, size-dependent conversion is found and can be explained by the looseness or thermal vibrations of the crystal lattice. 

Polydiacetylenes are conjugated polymers which can be in a planar or non-planar conformation depending on temperature. The planar-non-planar transition can be regarded as a rod-coil transition. The rod phase of polydiacetylene (4-butoxycarbonyl-methylurethane) (PDA) 4BCMU in dilute solution has been identified as the trans isomer and... 

The gel-sol transition temperature of (PDA) 4BCMU ( 70 C) is independent of polymer concentration. The lowest concentration in toluene where gel formation was observed is 0.06 wt%. Gels of (PDA) 4BCM exhibit optical birefringence which results from a spontaneous nematic alignment in the gel supported by hydrogen bonding [43]. 

Since polydiacetylene 4BCMU has a rodlike conformation with a large axial ratio (length/diameter) in certain solvents, it is a likely candidate for a lyotropic polymer. However, it has low solubility in those solvents and no liquid crystalline phase has been observed. As described above, a rod-to-coil conformational transition can be induced in the PDA 4BCMU by changing the solvent... 

Figure 9. Photograph of He-Ne laser beam as it passes through the PDA 4BCMU gel viewing direction is normal to propagation direction.

Signal from the photodiode. Thus, we measured th response of the system at the frequency of the oscillating electric field. In Fig. 10 we show the result for a = 0.5-wt.% gel of PDA (4BCMU) in toluene. One sees five equally separated resonances. Using the resonance condition for zero displacement at the boundaries n( /2) = d where is the wavelength of the nth mode, we obtain the slow wave sound velocity (v ) from the simple normal-mode equation v (v A ) = n (v /2d). From Fig. 10, v s 33 cm s. ... 

Table 6.6 Excited-State Parameters for PDA-PTS Crystals and PDA-4BCMU Films...

The lower panel in Fig. 6.11 shows the THG intensity and phase d (= tan Im/Re) of PDA-4BCMU films [100]. The largest SOS contribution, Eq. (30), is for A states with transition dipoles to IB. The prominent three-photon resonance at w = Eia/3 h is typical of conjugated polymers, and, as in /3-carotene [101,102], resembles the linear absorption. The indicated fit [95], with scaled intensity, is the Condon approximation for two g modes and displacements in Table 6.6. Contribu-... 

Fig. 6.11 Top Linear absorption (dashed line) of PDA-4BCMU films at 300 K and scaled fit (solid line) to IB in Table 6.6 the lines are 0-0, 0-1, and 0-2 Franck-Condon factors for C=C and C=C vibrations. Bottom THG intensity (open circles) and phase (closed circles) of the same films (from Ref. 100). Solid lines are based on Table 6.6 the dashed line is the THG intensity when 2A is deleted (/J-2AIB = 0) (from Ref. 105).

Fig. 6.13 Amplitude and phase of NDFWM spectra of PDA-4BCMU films (from Ref. 100) at (02 = 0.651 and 1.165 eV solid lines are based on Table 6.1. Raman resonances appear when o> -a>2 = 0.20 or 0.26 eV matches a C—C stretch. (From Ref. 95.)...

Etemad, and Z. G. Soos, Exciton relaxation in PDA- 122. 4BCMU from crystals to films, in Conjugated Polymeric Materials Opportunities in Electronics, Opto- 123. electronics, and Molecular Electronics (J. L. Bredas 124. and R. R. Chance, eds.), NATO ASI Ser. E, Vol,... 

There exist very few data on optical Kerr effect measurements in conjugated polymers. Ho et al.(1986) have studied optical Kerr effect in PDA poly-4BCMU solutions in CH2C- 2 PMMA matrix finding a large one... 

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