Poly 2.2 paracyclophane

Ulanski et al. (1990) described hole mobilities of poly(paracyclophane) (PDE) and PDE doped with 4% tetracyanoethylene (TCNE). The field dependencies were described as log i < E. The temperature dependencies were described by an Arrhenius relationship with a field-dependent activation energy. For PDE, the zero-field energy was 0.80 eV. The incorporation of TCNE resulted in an increase in mobility of approximately an order of magnitude. The authors suggested that this is caused by a decrease in the plane-to-plane distance in a cyclophane unit due to complexing with TCNE. 

Vogtle et al. have prepared chiral poly(imine) dendrimers of various generations by condensation of non-racemic 5-formyl-4-hydroxy[2.2]paracyclophane moieties with poly(amine) dendrimers [71]. They have found that the optical activity of these dendrimers was nearly constant with increasing generation number. 

Polymeric pseudocrown ether networks have been generated in situ by the photopolymerization of poly(ethylene glycol) diacrylate transition metal complexes <00CM633>, and the effect of metal ion templation was evaluated. The 1,6,13,18-tetraoxa[6.6]paracyclophane-3,15-diyne (termed pyxophanes) was prepared from hydroquinone and l,4-dichlorobut-2-yne it forms size-selective 7i-complexes with alkali metal cations <00CC2377>. Dibenzo[ ]crown-m have been used in numerous elegant studies in which they were the needles that were threaded by diverse reagents the resultant... 

Poly(l,4-naphthylenevinylenes) have been prepared by metathesis polymerization of benzobarrelenes [181,182] and the photoluminescence properties of homopolymers and block-copolymers have been studied in some detail [183]. PPV also has been prepared via ROMP of [2.2]paracyclophane-l,9-diene [184] and ROMP of a paracyclophene that contains a solubilizing leaving group [185]. The resulting polymer is converted to PPV upon acid catalysis at room temperature. ADMET of 2,5-dialkyl-l,4-divinylbenzenes using Mo or W catalysts has... 

J. Wiesecke and M. Rehahn, [2,2]Paracyclophanes with defined substitution pattern — key compounds for the mechanistic understanding of the Gilch reaction to poly(p-phenylene vinylene), Angew. Chem. Int. Ed., 42 567-570, 2003. 

Diederich and coworkers [10] synthesized so-called dendrophanes (Figure 13.6) containing a paracyclophane core embedded in dendritic poly(ether-amide) shells. X-ray crystal-structure analysis indicated that these dendrimers had an open cavity binding site in the center, suitable for the binding of aromatic guests. NMR and fluorescence titration experiments revealed a site specific binding between these dendrimers and 6-(p-toluidino)naphthalene-2-sulfonate (TNS) with a 1 1 association. Also, the fluorescence spectral shift of TNS, which is... 

As expected, the 1H—NMR spectrum shows only one absorption in the aromatic region (r=2.7). This is shifted considerably compared with that of unsubstituted [2.2]paracyclophane (t=3.7). In the IR spectrum an intense band occurs at 718 cm-1, as is characteristic for other [2.2]paracyclophanes, e. g. methoxycarbonyl[2.2]paracyclophanes 8 and 9 35>, though it is absent in the spectrum of the linear poly-p-xylene (10). The parent hydrocarbon 2 shows this absorption, ascribed to the distorted aromatic rings, at 725 cm-1 36>. 

The high strain energy of [2.2]paracyclophane (see Section 2.1.) facilitates ring-opening of the molecule via cleavage of the benzyl-benzyl bonds. Pyrolysis at 400 °C affords p,p -dimethylbibenzyl (155) and p,p -di-methylstilbene 109h At 600 °C, p-xylylene (156) is formed it polymerizes spontaneously to the linear poly-p-xylylene (10) on condensation 110>. 

Wunderlich, 1975 Surendran et al., 1987]. The reaction is carried out by pyrolyzing/7-xylene at temperatures of up to 950°C (in the absence of oxygen) to yield di-/7-xylylene (LIU) (also named [2,2]-paracyclophane), which is isolated as a stable solid. Subsequent polymerization of di-/ -xylylene to poly(/ -xylylene) involves vaporization of di-/ -xylylene by heating to about 160°C at 1 torr (1.3 x 102 Pa) followed by cleavage to /7-xylylene diradical (LIV) by heating at 680°C at 0.5 torr. The diradical nature of /7-xylylene was shown by ESR and... 

MacGillivray s group has employed rigid bifunctional molecules [42], such as 1,3-dihydroxybenzene and 1,8-naphthalenedicarboxyHc acid [42a], as linear templates to organize reactants such as fra s-l,2-bis(4-pyridyl)ethylene via hydrogen bonds for single and multiple photoinduced [2+2] cycloadditions, for the template-controlled synthesis of a l,2,3,4-(4-pyridyl)cyclobutane] [42b] and also of paracyclophanes [42d]. Very recently, [ ]ladderanes ( =2,3) have been synthesized in the solid state by UV irradiation of 2(5-methoxyresorci-nol) 2(4-pyr-poly-m-ene) (m=2,3) [42e]. 

The ROMP of [2.2]paracyclophane-l,9-diene (128) yields poly(p-phenylenevinylene) (129) as an insoluble yellow fluorescent powder. Soluble copolymers can be made by the ROMP of 128 in the presence of an excess of cyclopentene387, cycloocta-1,5-diene388 or cyclooctene389. The UV/vis absorption spectra of the copolymers with cyclooctene show separate peaks for sequences of one, two and three p-phenylene-vinylene units at 290, 345 and about 390 nm respectively, with a Bernoullian distribution. The formation of the odd members of this series must involve dissection of the two halves of the original monomer units by secondary metathesis reactions. 

By cathodic 1,6-dehalogenation p-xylylenes were prepared. When OLfxpifil,d-- hexachloro-p-xylene was electrolyzed at low temperatures the tetrachloro-p-xy-lene could be isolated 3231. Cpe of a, a+dibromo-p-xylene at the plateau of the first or second polarographic wave yields 5-10% [2.2] -paracyclophane and 90% poly-p-xylylene as products from the reactive unsubstituted p-xylylene (Eq. 

Paracyclophane-1,9-diene is an interesting cyclic diene monomer with a very strained ring. It has been easily polymerised with a tungsten carbene complex [148] to low molecular weight poly(p-phenylene vinylene) [148] ... 

Gorham 43 45 synthesized poly-p-xylylene(poly-QM) by a new technique involving vacuum pyrolysis of [2,2]-paracyclophane, cyclo-di-xylene (cyclo-di-QM) at 600 °C. When the pyrolyzed gas of cyclo-di-QM, namely QM, is condensed on glass or... 

Paracyclophanes, table, 47 Para formaldehyde (poly oxy methylene), 88... 

Poly-paraxylylenes are deposited by a thermal CVD process popular in the microelectronics industry as the "Gorham process"." The starting material for this deposition process (precursor) is usually a paracyclophane dimer (DPX). The dimer dissociates to form reactive monomer species, which then undergoes nucleation and growth leading to polymer thin film formation. The following reaction ensues ... 

A number of other unsaturated poiyhydrocarbons have practical applications. These include poiy(phenyl acetylene) and poly((E,E)-[6.2]paracyclophane-1,5-diene), which have been studied as photoconducting polymers. The thermal decomposition of polyacetylenes and of poly((E,E)-[6.2]paracyclophane-1,5-diene) generates fragments summarized in Table 7.1.8 [19]. 

Table 7.1.8. Summary regarding thermal decomposition of polyacetylene and of poly((E,E)-[6.2]paracyclophane-1,5-diene) [19],...

Poly(St-C3 St) obtained by cationic initiators has the same characteristic spectroscopic properties as [3.3]paracyclophane. 

It is known that [3.3]paracyclophane, which has the almost highest transannular interaction of the less distorted benzenes (12), has the fluorescence emission at longer wavelength (356 nm) (18) than the excimer of 1,3-diphenylpropane (332 nm). The fluorescence spectrum of the cyclopolymer, poly(St-C3-St), recorded under the same conditions as for [3.3]paracyclophane is illustrated in Figure 1 (20). Both have the fluorescence at the same wavelength, and therefore the polymer is supported to contain [3.3]paracyclophane units as sequence units. The fluorescence emission at 312 nm is ascribed to the residual styryl groups. 

The structure of poly(St-C3 St) can be also clarified by 13C-NMR spectroscopy. Although the polymer gave a rather complicated spectrum, carbons in the linkage and a part of aromatic carbons, numbered from 1 to 4 in the structure illustrated in equation (1), were able to be assigned easily. The chemical shifts of these carbons are almost the same as those of [3,3]paracyclophane. 

Organometallic derivatives of poly-p-xylylene (PPX) with Ge and Sn atoms covalently bonded to polymer chains have been synthesized by a vapor deposition technique using bridged [2,2]-paracyclophanes with corresponding organometallic groups [32, 33]. Pyrolysis of these cyclophanes, along with polymerization of the /7-xylylene monomer mixture, is shown in Scheme 2.2. 

The conventional fabrication process for poly(tetrafluoro-p-xylylene) (Par-ylene F) is difficult, involving many process steps, and is more expensive than that for Parylene N. Typically, this process first involves the formation of a dimer, l,l,2,2,9,9,10,10-octafluoro[2.2]paracyclophane. The dimers are cracked at 720-730°C to get the monomer TFPX. 

Dichloro[2.2]-paracyclophane Figure 3.2 Monomers Used for Poly(p-phenylene vinylene)... 

Disiloxane-functionalized [2.2]paracyclophane can be polymerized to a siloxane-substituted poly-(p-xylylene) by a CVD polymerization technique [46]. The basic mechanism is shown in Figure 2.4. 

---