Polynorbornene

One of the most interesting of the newer elastomers is the aromatic equivalent of a polyalkenamer, polynorbornene, which is used in its plasticized form. Its introduction followed about 10 years of study of the Diels-Alder reactions of olefins with cyclopentadiene undertaken by CdF Chimie in France. In 1976 this company put on stream a plant with a capacity of 5000 tonnes per annum to produce the polymer which they market as Norsorex. 

The monomer, norbornene (or bicyclo 2,2,l-heptene-2) is produced by the Diels-Alder addition of ethylene to cyclopentadiene. This is then polymerized by a ring-opening mechanism to give a linear polymer with a repeat unit containing both an in-chain p-phenylene group and a double bond. Both cis- and trans- structures are obtainable according to the choice of catalyst used (Le Delliou, 1977). 

The polymer has a T, of about +35°C and is thus not rubbery at usual ambient temperatures. If however it is blended (plasticized) with an aromatic oil or an ester plasticizer a rubbery material is obtained. The T, of the polymer-plasticizer blend can be as low as 

Several of the bibliographical references are to chapters in The Polymer Chemistry of Synthetic Elastomers, edited by J. P. Kennedy and E. G. M. Tornqvist, Interscience, New York, Part 1 (1968) and Part 2 (1969). These chapters all contain a comprehensive list of references and provide excellent summaries of the state of the art up to the late 1960s. 

Peak Notation Assignment of Main Peaks Molecular Weight Retention Index Relative Intensity 

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The polynorbornenes X bearing cyclotriphosphazenes with -0(CH2CH20)x-CH3 (x=l, 2,3,7.2) side groups have been prepared via ring opening metathesis polymerization (ROMP) and complexed with LiS03Cp3 and LiN(S02Cp3)2 (10-60% molar ratios) by Allcock [619,620]. 

The mechanical properties of X depend partly on the length of the oli-goethyleneoxy groups. The polymers are solid for x=l, highly viscous gums for x=3 and elastomers for x=7.2. The maximum conductivity of these complexes at 30 °C are reported in Table 16. Gel electrolytes have also been obtained by adding propylene carbonate (PC) (10-50 wt%) to these polynorbornene de-... 

Table 16 Maximum conductivity of polynorbornenes bearing cyclotriphosphazenes/lithium salt systems at 30 °C...

Polynorbornene is not oil resistant, and solvents which can extract the plasticiser will obviously be detrimental to its performance. 

Many of the studies concerning ring-opening metathesis by well-characterized metathesis catalysts have employed substituted norbornenes or norborna-dienes. Substituted norbornenes and norbornadienes are readily available in wide variety, and they usually react irreversibly with an alkylidene. Norbornene itself is the most reactive, and the resulting polynorbornene probably is the most susceptible to secondary metathesis. Formation of polynorbornene often is used as the test reaction for ROMP activity. ROMP by well-defined species has been reviewed relatively recently [30], so only highlights and selected background material will be covered here. 

The first report of ROMP activity by a well-characterized Mo or W species was polymerization of norbornene initiated by W(CH-t-Bu)(NAr)(0-f-Bu)2 [122]. In the studies that followed, functionality tolerance, the synthesis of block copolymers, and ring-opening of other monomers were explored [30, 123]. Two important issues in ROMP concern the cis or trans nature of the double bond formed in the polymer and the polymer s tacticity. Tacticity is a consequence of the presence of two asymmetric carbons with opposite configuration in each monomer unit. The four ROMP polymers (using polynorbornene as an example) that have a regular structure are shown in Scheme 3. 

Scheme 3. The four possible regular structures of polynorbornene prepared by ring-opening metathesis polymerization...

D. Lee, M. C. Choi, C. S. Ha, Polynorbornene dicarboximide/amine functionalized graphene hybrids for potential oxygen barrier films., Journal of Polymer Science Part a-Polymer Chemistry, vol. 50, pp. 1611-1621, 2012. 

Pollino JM, Week M. Supramolecular side-chain functionalized polymers synthesis and self-assembly behavior of polynorbornenes bearing Pd SCS pincer complexes. Synthesis 2002 9 1277-1285. 

Functionalized polynorbornene derivatives, (V), prepared by Liaw et al. (4) using ring-opening metathesis polymerization exhibited strong carbazole fluorescence. Monomer emissions occurred in the near ultraviolet (UV) at approximately 380 nm and extended into the blue-violet region at 330 nm. 

Sequential addition methods were utilized to synthesize block copolymers of polybenzvalene with polynorbornene to yield block copolymers of PA and pol-ynorbornene after isomerization [43]. (It should be noted that both benzvalene and polybenzvalenes are sensitive to shock and mechanical stress causing ring strain-promoted explosions in the precursor materials.)... 

Fig. 1.20 Functionalization strategy for a polynorbornene (PNBE) coating of SWCNTs. Path A adsorption of organic precursors (a)...

A patent by A. W. Anderson et al. (Du Pont) disclosed the first transition metal catalyzed polymerization of a cyclic olefin in 1955 [1]. Subsequent to the discovery of Ziegler-Natta polymerization [2] norbornene was found to polymerize in the presence of the catalyst systems TiCl /EtMgBr. Eleuterio [3 a] and Truett et al. [3 b] obtained polynorbornene by using transition metal catalysts based on Mo and Ti, respectively. IR-studies and ozonolysis of the polymer revealed the presence of carbon-carbon double bonds, indicating that polymerization had occured by unexpected ring opening Eq. 1 [3]. 

Two ended living polynorbornene 23 was prepared with difunctional initiator 22a, b, and anti-7,8-benzotricyclo[4.2.2.02,5]deca-3,7,9-triene 26 was added as a second monomer to produce a triblock copolymer with a poly(norbornene) middle segment, Eq. (29) [42b]. Naphthalene cleavage occured upon heating to temperatures above 120 °C. The product of thermolysis is polyacetylene/polynorbor-nene/-polyacetylene triblock copolymer 28. 

The DIPP tantalacyclobutane complex, 32a, has been shown to polymerize excess norbornene at 50 °C to yield polynorbornene with a molecular weight... 

The catalytic activity for olefin polymerization was evaluated for complex 17a. High molecular weight addition-type polynorbornene (PNB) with a moderate molecular weight distribution (Mw = 106, Mw/Mn = 2.3-3.5) was obtained when 17a was activated with MAO. The activity was highest at 80 °C (107 g of PNB/(mol of Ni) h 1) resulting from an increase in the concentration of active catalyst centers at that temperature. However, further increases in temperature led to catalyst decomposition rather than higher turnover numbers. 

Norbornene and norbornene methyl ester have been polymerized forming a polymer that lacks backbone carbon-carbon double-bond unsaturation. The polymerization catalyst mixture consisted of palladium acetate, a phosphine such as tricyclohex-ylphosphine, a Lewis acid such as dimethyl zinc, and hexafluoroisopropanol. Polynorbornenes prepared in this manner typically had M s> 200,000 daltons with polydispersies less than 2, while poly(norbornene methyl ester) had M s of roughly 100,000 daltons. 

Norbornene polymerization CdF Chimie Elf Atochem operated since 1976 Nippon Zeon 2 steps operated since 1991 norbornene norbornene polynorbornene (Norsorex ) hydrogenated norbornene (Zeonex ) RuCls/HCl/BuOH 25-100°C... 

Fig. 5 Eight possible diads for a ( )-trans-2,3 disubstituted polynorbornene chain the X substituent is derived from the exo-position, N from the endo position in the monomer...

One example of a 1 1 AB block copolymer with poly-(IX-8) and poly-(X-S) blocks showed a smectic A phase the mesophase of the homopolymer of X-8. The more ordered smectic A phase dominated the nematic phase of the polynorbornene block. 

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