Copolymers with intrinsic

Classification by the Absorber. Polymers can have intrinsic absorption at the irradiation wavelength or a dopant can be used to induce the necessary absorption. The dopant can be implemented either into the polymer matrix on a molecular level or as absorber particles in the nanometer to micrometer range. The absorbing species can also be included into the polymer backbone or side chains to increase the absorption and thereby forms a copolymer with intrinsic absorption. 

It is worth mentioning that the extent of induced circular dichroism on NVC units when inserted in copolymers with intrinsically chiral comonomers is of the same order of magnitude as that extrinsically induced by thermotropic cholesteric mesophases on achiral 9-ethylcarbazole when physically trapped within the mesophase . Higher extrinsic circular dichroism effects are by contrast reported when lyotropic cholesteric mesophases, such as those obtained from polyfy-benzylglutamate) in tetrachloroethane, are used as chiral traps of achiral carbazole derivatives and iso-electronic aromatic compounds ... 

The polymer samples studied here fall into three distinct categories. Data from two sample populations have been combined in the SAN copolymer study. A group of SAN materials having compositions ranging from 42 (wt)% AN to 82% AN were polymerized and characterized quite some time ago (1972), with intrinsic viscosities determined only in DMF. Very recently, a second group of SAN s with compositions from 5 (wt)% to 48% AN, as well as one sample of polystyrene (0% AN), were polymerized and characterized, with intrinsic viscosities determined in DMF, THF, and MEK. These two populations are differentiated in the Results section by the designations "old data" and "new data". The third category of samples is that of S/MA copolymers and S/MA/MM terpolymers, with intrinsic viscosities measured only in MEK. 

An AB monomer, 2-(4-hydroxyphenyl)-3-phenyl-6-fluoroquinoxaline [17], was prepared from the reaction of 4-hydroxybenzil and l,2-diamino-4-fluorobenzene and subsequently polymerized under aromatic nucleophilic displacement conditions in NMP. The resultant polymer exhibited an intrinsic viscosity of 1.23 dL/g, a Tg of 247 °C and thin film tensile strength and modulus at room temperature of 107 Mpa and 3.2 GPa, respectively [17]. The same AB monomer was also copolymerized with hydroquinone and 4,4 -difluorodiphenyl sulfone to yield a series of copolymers with interesting properties [17]. The same AB monomer was prepared and polymerized by other researchers to yield a polymer with an intrinsic viscosity of 0.65 dL/g and a Tg of 255 °C [18]. 

Procedure 3 Oxidation of MPP with Redissolved DPP Homopolymer. A mixture of 7.3 grams of MPP and 9.8 grams of DPP homopolymer was oxidized for 15 minutes at 30°C, as described in the previous examples, yielding 86% of copolymer, with an intrinsic viscosity of 0.48 dl/g. 

Here the subscript i refers to the solvent, whereas the superscript (A or B) refers to the component homopolymer. For example, ai is the thermal diffusion coefficient of a homopolymer consisting of component B in solvent 1. Parameters [rj]i and Xi are the intrinsic viscosity and retention parameter measured on the copolymer in solvent i T g in equation 9c is the temperature at the center of gravity of the retained polymer zone in solvent i, while rjo is the viscosity of solvent i at Teg- Equations 7 through 9 are applicable to copolymers with only two components similar equations could be derived for n-component copolymers, in which case My and Xa are determined from retention and viscosity data in n separate solvents. 

Extensive work with condensation polymers and copolymers fully confirms the importance of structural regularity on crystallization tendency, and consequently on associated properties. Thus, copolymers containing regular alteration of each copolymer unit, either ABABAB type or block type, show a distinct tendency to crystallize, and corresponding copolymers with random distributions of the two are intrinsically amorphous, less rigid, lower melting, and more soluble. 

The synthesis of block copolymers is particularly suited to investigate the combination of two fundamentally different synthetic techniques, since the marriage of two chemically different building blocks often requires a considerable synthetic effort. Block copolymers with building blocks based on two intrinsically different polymerization mechanisms, e.g. polyester and polymethacrylate, can... 

Yang, Z., Karasz, E., and Geise, H. J. 1993. Intrinsically soluble copolymers with well-defined alternating substituted p-phenylenevinylene and ethylene oxide blocks. Macromolecules 26 6570-6575. 

Finally we mention that draw-induced mesophases have also been observed in some other semi-rigid chain polymers. Examples of such studies are cold drawing of glassy PEN [108,109] and oriented crystallization of PET/PEN copolymers [110, 111]. In all cases a smectic mesophase has been reported. In the absence of crystallization it can attain a degree of stability that resists decay from chain relaxation. This supports the view that the mesophase represents a thermodynamic state [101]. We expect that similar mesophases based on semi-rigid monomers can be observed in other polymers with intrinsic rigid building blocks, such as other aromatic polyesters and polyamides. 

Copolymers with arylene-ethynylene and arylene-vinylene units combine the intrinsic features of both moieties in a single polymeric backbone [147]. 

Huang, H. and P.G. Pickup. 1998. A donor-acceptor conducting copolymer with a very low band gap and high intrinsic conductivity. Chem Mater 10 2212. 

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