Polynorbornene study

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. 

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]. 

Al-Badri and co-workers [55] studied the effect of fine-tuning the cationic parameter of synthetic mimics of antimicrobial peptides (SMAMP) on haemolytic and antibacterial activities. A category of novel norbornene monomers that carry one, two or three Boc-protected amine-functionalities was synthesised (Figure 3.8). ROMP of the monomers, followed by deprotection of the amine groups led to cationic antimicrobial polynorbornenes that carry one, two and three charges per monomer repeat unit. It was observed that enhancing the number of amine groups on the most hydrophobic polymer effectively decreased its haemolytic activity. 

Antibiotic-resistant bacteria cause life-threatening infections in hospitals and society in general. There is a vital requirement to develop new antimicrobial agents, but this task involves extensive scientific trials. This chapter reviewed broad-spectrum polymeric antimicrobials, which are not susceptible to current resistance, and mechanisms of bacteria to mimic the antimicrobial action of natural HDP, which exert their effect by permeabilising the bacterial cytoplasmic membrane. Most cationic antimicrobial polymers appear to work in a manner similar to membrane-active AMP, such as magainin. The design and synthesis of different polymers, such as methacrylate-based copolymers, PPE, polynorbornene by-products, amphiphilc arylamide polymers and large polymers, have been studied as biomimetic polymers in different applications. 

Tew and co-workers studied the biological activities of antimicrobial polymers and found that they were influenced by the amphiphilicity of the polymer or oligomer as an entity rather than the activity of one antimicrobial portion, either embedded or covalently attached, and mostly contained antimicrobial macromolecules that can mimic the biological action of antimicrobial natural host-defence peptides (e.g., synthetic polyphenylene ethynylenes, polynorbornenes and polymethacrylates) [4]. 

Recently, Sannino and co-workers studied the activity of Grubbs catalyst- functionalized MWCNTs by the ROMP synthesis of polynorbornene. The activities of the and 2 generation Grubbs catalysts loaded on to CNTs were found to be similar in the ROMP of 2-norbornene. The eharacterization of polynorbornene-CNT composites confirmed the good dispersibility of the nanotubes in the polymer matrix. ... 

Addition-type Polynorbornene with Si(CH3)3 Side Groups Detailed Study of Gas Permeation, Free Volume and Thermodynamic Properties... 

To conclude this section, an example is given of the application of statistical models to examine double bond sequences in polymers with unsaturated backbones. The presence of backbone unsaturation leads to the occurrence of cisitrans isomerism and this can be treated entirely analogously to comonomer sequence. Ivin [42] and others have used NMR spectroscopy extensively to study the microstructure of polymers prepared by transition metal catalysed ring-opening metathesis polymerisation (ROMP) such as polynorbornene (PNB). 

Cataldo, F. FT-IR spectroscopic characterization of hydrogenated polyoctenamer and polynorbornene and DSC study of their thermal properties. Polym. Int. 1994, 34, 49-57. 

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. 

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