Polymer color changes

Polymer Color change Applied voltage (V) Cycle lifetime... 

Polymerization in Bilayers. Upon irradiation with UV light the monomer vesicles are transferred to polymer vesicles (Figure 12.). In the case of the diyne monomers (2,5-9,12,13,14) the polyreaction can again be followed by the color change via blue to red except phospholipids (5,6), which turn red without going through the blue intermediate as observed in monolayers. The VIS spectra of these polymer vesicle dispersions are qualitatively identical to those of the polymer monolayers (Figure 13.). 

As a result, an insolnble transparent blue polymer film forms on the electrode. Electrochemical oxidation of the film in acetonitrile initiates a rapid color change from bine to pale gray, while redaction to the first or second cathodic waves causes the film to become pale green or orange, respectively. These electrochromic effects are stable and reversible when air and water are excluded, even after 30,000 rednction cycles. The material has potential uses in electrochromic or electroluminescent devices. 

Figure 8.7 Schematic representation of the recombinations of polymer 29 and 30 to obtain visual color changes (a) in solution and (b) in neat [26].

The addition of water to solutions of PBT dissolved in a strong acid (MSA) causes phase separation in qualitative accord with that predicted by the lattice model of Flory (17). In particular, with the addition of a sufficient amount of water the phase separation produces a state that appears to be a mixture of a concentrated ordered phase and a dilute disordered phase. If the amount of water has not led to deprotonation (marked by a color change) then the birefringent ordered phase may be reversibly transformed to an isotropic disordered phase by increased temperature. This behavior is in accord with phase separation in the wide biphasic gap predicted theoretically (e.g., see Figure 8). The phase separation appears to occur spinodally, with the formation of an ordered, concentrated phase that would exist with a fibrillar morphology. This tendency may be related to the appearance of fibrillar morphology in fibers and films of such polymers prepared by solution processing. 

Note 1 Examples of the changes in photosensitive polymers are a change in molecular shape (photoresponsive polymer), a change in its constitution (photoreactive polymer), and a reversible change in color (photochromic polymer). 

A number of poly(arylene vinylene) (PAV) derivatives have been prepared. Attachment of electron-donating substituents, such as dimethoxy groups (structure 19.3), acts to stabilize the doped cationic form and thus lower the ionization potential. These polymers exhibit both solvatochromism (color changes as solvent is changed) and thermochromism (color is temperature-dependent). 

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