4BCMU

At this time, many of the parameters listed above have not been measured for nonlinear organic materials. Measurement will be necessary for an assessment of the full potential of such materials. To date, only a nonlinear directional coupler has been implemented in a nonlinear polymer, (poly-4BCMU). For this device at 1060 nm, the nonlinear response was dominated by two-photon absorption, and some limited switching attributable to absorption changes was observed (27). More recent work at 1030 nm appeared to show switching attributable to refractive nonlinearities (28). Clearly there is much progress to be made. 

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.

Figure 21 Absorption spectrum of poly-4BCMU chains at 20 K. (From Ref. 118.)...

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... 

Though the quantum yield for photopolymerization with UV light is high at low polymer conversions, it rapidly decreases as the polymer concentration increases [2). The limiting yield for UV polymerization in 4BCMU is about 35%. It is believed that this effect has its origin in quenching of the monomer excited states by the polymer chains, i.e., the monomer excited states created on irradi-... 

Figure 5.11. Change of the absorption spectra of p-4BCMU in toluene under cooling. The yellow solution corresponds to a maximum absorption located at 4600 A, the red phase at...

The values for functionalized polymers, listed in Table 2 compare also well with conjugated polymers which form good optical quality amorphous thin films like polydiacetylene poly-4BCMU and functionalized polythiophenes po-ly(3-decyl)thiophene (P3DT) and poly(4-,4 -didecyl-2,2 Ibithiophene (PDDBT)... 

Table n. Molecular Weight of Poly(4BCMU) Microcrystals... 

Figure 4. SEM photographs of poly(4BCMU) microcrystals with average size of (a) 1 fim. and (b) 300 nm.

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]. 

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