Chain copolymers

Figures 12-12 and 12-13 document that trap-free SCL-conduction can, in fact, also be observed in the case of electron transport. Data in Figure 12-12 were obtained for a single layer of polystyrene with a CF -substituted vinylquateiphenyl chain copolymer, sandwiched between an ITO anode and a calcium cathode and given that oxidation and reduction potentials of the material majority curriers can only be electrons. Data analysis in terms of Eq. (12.5) yields an electron mobility of 8xl0 ycm2 V 1 s . The rather low value is due to the dilution of the charge carrying moiety. The obvious reason why in this case no trap-limited SCL conduction is observed is that the ClVquatciphenyl. substituent is not susceptible to chemical oxidation.

For flexible chain copolymers based on acrylic and methacrylic acids (AA and MA) crosslinked with a polyvinyl component, the inhomogeneity of the structures formed depends on the nature of the crosslinking agent, its content in the reaction mixture and the thermodynamic quality of the solvent [13,14],... 

As already shown, it is technically possible to incorporate additive functional groups within the structure of a polymer itself, thus dispensing with easily extractable small-molecular additives. However, the various attempts of incorporation of additive functionalities into the polymer chain, by copolymerisation or free radical initiated grafting, have not yet led to widespread practical use, mainly for economical reasons. Many macromolecular stabiliser-functionalised systems and reactive stabiliser-functionalised monomers have been described (cf. ref. [576]). Examples are bound-in chromophores, e.g. the benzotriazole moiety incorporated into polymers [577,578], but also copolymerisation with special monomers containing an inhibitor structural unit, leading to the incorporation of the antioxidant into the polymer chain. Copolymers of styrene and benzophenone-type UV stabilisers have been described [579]. Chemical combination of an antioxidant with the polymer leads to a high degree of resistance to (oil) extraction. 

Later, Kallitsis and coworkers reported similar PPP copolymers, with oligophenylene blocks separated by nonconjugated aliphatic chains. Copolymers 496 [595], 497 and 498 [596] contained the oligophenylene blocks in a main chain or as pendant substituents,... 

Just as with other conjugated polymers, the emission color of PPE can be tuned by introducing different conjugated fragments in the polymer chain (copolymers 523 and 524) [627,638], Thus, red-orange EL (AEL 590 nm and a shoulder at 530 nm) was reported for the anthracene-based polymer 523 (in PLED ITO/523/A1), whereas... 

Statistical co-crystallization of different constitutional repeating units, which may either belong to the same copolymer chains (copolymer isomorphism) or originate from different homopolymer chains (homopolymer isomorphism). 

APPLICATIONS OF NONCOVALENTLY FUNCTIONALIZED SIDE CHAIN COPOLYMERS... 

APPLICATIONS OF NONCOVALENTLY FUNOTIONALIZED SIDE CHAIN COPOLYMERS 125... 

Figure 11.18 Dendron chain copolymers, (a) A poly ether dendron displaying a focal PEG chain and (b) notional representation of the self-assembly of the dendron chain copolymers.

The crown ether adopts a D3d conformation and is coordinated on both faces by NH3 groups from centrosymmetrically related Cu++ complexes. The trans NH3 groups each bind to a crown ether forming long chain copolymers. In addition to the NH3... 

All polymers discussed so far are homopolymers, i.e., they consist of multiple sequences of the same repeating unit. Regular linear homopolymers without bulky pendant groups, such as hdpe, are easily crystallized. However, the tendency for crystallization is reduced in copolymers, since they contain more than one repeating unit in the chain. Copolymers with random arrangements of repeating units in the polymer chain are generally amorphous. 

The composition of the grafted side chain copolymer has also been determined by Sakurada (113) and found to be different from the normal copolymer formed with acrylonitrile and butadiene. With styrene the grafted copolymers were found to be richer in acrylonitrile than the normal copolymer. Similar differences were found by Resting (114) with methyl methacrylate and styrene grafted to cotton and by Odian et al. (115) with grafting mixed monomers to Teflon and to polyethylene. It is believed that one monomer may be preferentially sorbed or diffused faster than the other, leading to a different monomer ratio at the actual site of grafting. 

However, in some cases, additional effects on (dn/dc)copo must be considered. Due to cooperative interactions between the monomer units in the polymer chain, copolymer refractive index increments may deviate from the summation scheme. As a result of different sequence length distributions, different values of (dn/dc)copo can be obtained for the same gross composition. Copolymer (dn/dc)copo values can be obtained by multiple detection SEC providing the chemical composition at each slice of the elution curve. 

Copolymerization is a variant of polymerization where macromolecules composed of two or more kinds of monomer are formed. According to the frequency of entry of various monomers into the chains, copolymers (and even the reactions by which they are formed) are sometimes more closely specified by special attributes. Thus copolymers may be unspecified, statistical, random, periodic, alternating, block or graft. 

FIG. 5.5 Range of compositions favoring the formation of the fsoSm phase for chiral azo dye side-chain copolymers. 

Kozlovsky, M. V., Fodor-Csorba, K., Bata, L., Shibaey, V. P. Chiral smectic side-chain copolymers. 1. Synthesis and phase behavior, Eur. Foiym. /. 28, 901 (1992). 

Demikhov, E., Kozlovsky, M. V, Amorphous chiral smectic A phase of side-chain copolymers. Liquid Crystals 18, 911 (1995). 

Kozlovsky, M. V., Meier, J. G., and Stumpe, J. Chiral side-chain copolymers. 4. Kinetics of the phase transition from conventional isotropic liquid to the TGB-like isotropic smectic state. Macromol. Chem. Phys. 201, 2377 (20()0). 

Very low-angle X-ray data (26 A resolution) of horse spleen apoferritin fit approximately the Fourier transform of a uniform spherical shell with inner and outer diameters of 76 and 122 A (92, 95). Low-angle difference X-ray data for ferritin and apoferritin indicate iron cores of high scattering power that are approximately spherical (d = 78 A) (92). Cubic crystal point symmetry shows that ferritin molecules are composed of 24 structurally equivalent subunits related by 432 symmetry, there being one polypeptide chain per asymmetric unit. In mixed H and L chain copolymers, the apparent structural equivalence must be statistical, although very similar chain conformations are expected. 

In fact, the photochemical process Is much less sensitive to the rigidity of the system if the azobenzene Is attached as a side chain. Copolymer ABA-MMA exhibited a quantum efficiency only 4-5 times lower In a glassy film then in dilute solution ( ). By contrast. Figure 3 shows the relative quantum efficiencies for the trans-cls Isomerization of a copolyamlde of Isophthallc acid with 4,4 -dlamlnodlphenyl sulfone containing a small proportion of... 

Side-chain copolymers. This approach (Fig. 8.Id) is the inverse application of the strategy described in the previous paragraph. The backbone is a soluble nonconjugated polymer, whereas para-phenylene molecules are attached to it. For this approach, there is a fundamental limit in both the number and the length of the attached para-phcnylcne molecules exceeding this limit results in the loss of solubility. 

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