Monomers, acetylene terminated

Rezac, M. E., and Schoberl, B. (1999). Transport and thermal properties of poly (ether imide)/acetylene-terminated monomer blends, J. Membrane Sci. 156, 211. 

A distinctive feature of PABs is that synthesis can easily be carried out from diethynylarenes as the monomer by the Hay method (Scheme 10.1(A)) affording acetylene-terminated PABs in high yield without defects. For synthesis of an air-sensitive PAB, or for use as an air-sensitive monomer, a modified or alternative method can be applied to the reaction [24,38,39]. 

Fire relstance,chemical composition by infrared (IR) and nuclear magnetic resonance (Mlffit) spectroscopy, thermal analyses, Clash-Berg moduli determination and dynamical mechanical analyses were determined. The fluorenone polyesters were spun as fibers from solution. They were blended with an acetylene terminated fluorenone monomer for plasticization and crosslinking at high temperatures to form an improved thermally stable product. 

Acetylene terminated monomers, e.g., acetylene terminated sulfone are known to exhibit high thermal stability, good adhesion characteristics and high moisture resistance (.6,7). Starting with bls-phenol fluorenone we synthesized acetylene terminated fluorenone (ATF). 

Reactions of Hydrocarbons. Several types of reactive hydrocarbon functional groups can be used to polymerize and cross-Unk monomers and ohgomers into thermoset plastics. These include addition polymerization of acetylene-terminated molecules and ring-opening polymerization of strained carbon rings. They also include Friedel-Crafts condensation to form hydrocarbon polymers. 

Polysulfones have been made from acetylene-terminated sulfone monomers (Fig. 3.51), and cured graphite-fiber laminates have shown Tg = 300°C and good mechanical properties at 170°C before and after heat and humid aging. Semi-interpenetrating polymer networks with linear thermoplastic polysulfones showed promise of combining the heat deflection temperature and solvent-resistance of the thermoset polymer with the impact resistance of the thermoplastic. 

A substantial effort in this laboratory has been directed toward the synthesis and characterization of acetylene terminated oligomers for use as addition-curable, moisture-resistant, thermoset systems. Early work on the acetylene-terminated phenylquinoxalines demonstrated the moisture insensitivity of the product generated from the thermal cure. Studies of various difunctional acetylene-terminated monomers has demonstrated that the polymerization is a free radical propogation of the acetylene moiety to a linear conjugated polyene. 

Diacetylenes in phospholipid bilayers have been the subject of extensive studies in our laboratory, not only because of the highly conjugated polymers they form, but also because of their ability to transform bilayers into interesting microstructures. Consequent to our synthesis and characterization of several isomeric diacetylenic phospholipids, we have found that the polymerization in diacetylenic bilayers is not complete. In order to achieve participation of all diacetylenic lipid monomer in the polymerization process, diacetylenic phospholipid was mixed with a spacer lipid, which contained similar number of methylenes as were between the ester linkage and the diacetylene of the polymerizable lipid. Depending upon the composition of the mixtures different morphologies, ranging from tubules to liposomes, have been observed. Polymerization efficiency has been found to be dependent on the composition of the two lipids and in all cases the polymerization was more rapid and efficient than the pure diacetylenic system. We present the results on the polymerization properties of the diacetylenic phosphatidylcholines in the presence of a spacer lipid which is an acetylene-terminated phosphatidylcholine. 

Anticipating the discussion on acetylene polymerization [98], extensively reported in Section IV, a value of n = 0.6 has been found, which implies a linear diffusion-controlled growth where the molecular librational and translational oscillations control the approach of the monomers to the active sites (chain terminations). 

It was proved that metal carbynes are sources of metal carbenes [e.g. scheme (9) in Chapter 6] promoting the polymerisation of acetylenic monomers. Therefore, related metal carbynes and carbenes appeared to catalyse the polymerisation of alkynes in the same way as regards the identity of the products, in particular as regards stereochemistry. For the terminal and internal alkynes, the Fischer carbyne acts much like the Casey and Fischer metal carbenes. The Fischer carbyne also promotes acetylene polymerisation, and it does this where the Fischer carbene fails and the Casey carbene is much less effective [22,143]. 

As in the case of the ring-opening metathesis polymerisation of cycloolefins, an important matter is the control of polymerisation to prepare acetylenic polymers having precise structures. A living polymerisation is of practical importance in the synthesis of monodisperse polymers, such as terminally functionalised polymers and block copolymers. The metathesis catalysts that promote the living polymerisation of acetylene [42] and acetylenic monomers include M0OCI4 SnBu EtOFkNbCls and Ta, Mo and W alkylidenes [84, 133, 152, 153]. 

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