The strong Lewis acid B(C6F5)3 was found to activate complexes of nickel toward the polymerization of norbornene-type monomers. The active species in this reaction is created by the transfer of C 6F5 from boron to nickel. As a result, a class of neutral, single-component nickel complexes was developed containing two electron-withdrawing aryl ligands that polymerize norbornene and norbornenes with functional pendant groups. Active complexes include Ni(C 6F5)2(PPh2CH2C(O)Ph), (η 6 -toluene)Ni-(C6F5)2, and Ni(2,4,6-tris(trifluoromethyl)phenyl)2(1,2-dimethoxyethane). In the case of (η 6 -toluene)Ni-(C6F5)2, isolation and characterization of low molecular weight norbornene polymers, using ethylene, indicated that each polymer chain contained a C6F5 headgroup. This points to the initiation step as being the insertion of norbornene into the Ni-C6F5 bond. The polymer microstructure as revealed by 1 H and 13 C NMR spectrometry is entirely different from that produced using the cationic nickel catalyst, [(η 3crotyl)Ni(1,4-COD)]PF6. This difference in microstructure led to improved mechanical properties for 80: 20 copolymers of norbornene and 5-triethoxysilylnorbornene.

The copolymerization of ethene with norbornene derivatives, as well as their terpolymerization with 1-alkenes, using a series of neutral, square-planar nickel complexes containing anionic P∼O chelates is described. In copolymerizations, up to 50 mol % incorporation of norbornene, leading to an essentially alternating copolymer, is obtained. With norbornene derivatives bearing oxygen functionalities, the level of incorporation is lower, as are the reaction rates and polymer molecular weights. In the case of terpolymerization of ethene and norbornene with 1-alkenes, the polymer molecular weights tend to be low because of slower monomer insertion and additional chain-transfer pathways that are available following 1-alkene insertion. For the ethene/norbornene polymers synthesized, the glass transition temperature (T g) increases smoothly with increasing norbornene content. Solution-cast films of the polymers show good optical clarity.

SynopsisDifferent formulations of rubber with chopped coconut fiber (treated and untreated) as reinforcing agent were prepared. These reinforced systems were vulcanized at 153°C and the properties of the vulcanizates were studied by stress-strain, shore A hardness, and abrasion loss measurements. The bonding between the rubber and fillers were improved by the addition of bonding agents. The bonding effect of different bonding agents were compared. The reinforcing property of the treated fiber was compared with the untreated one. Aging resistance of the composites were studied. The fracture surfaces have been studied by scanning electronmicroscopy (SEM) and the failure mechanism has been explained.

The synthesis of bisphenol A–glycidyl methacrylate (BIS–GMA), the resin component in most dental composite restorative materials, catalyzed by different tertiary amine accelerators such as N,N′‐dimethyl‐p‐toluidine (DMPT), N,N′‐dimethylamino phenethyl alcohol (DMAPEA), and N,N′‐dimethylamino ethyl methacrylate (DMAEMA) is reported in this work. The effect of varying concentrations of accelerators and the reaction conditions of the synthesis as a function of time is studied in detail. The kinetics of the reaction between epoxide and carboxyl group during the formation of BIS–GMA is monitored using infrared (IR) and chemical techniques. The reaction is found to follow first‐order and zero‐order kinetics with respect to epoxide and acid, respectively. The degree of epoxide and acid conversion has been calculated as a function of time. The percentages of various isomers, formed under different reaction conditions have been reported. Characterization procedures for BIS–GMA have been developed.

Acta Polyrnerica 41 (090) Nr. 11 560 RAJALINUAM, RADHAKRISHNAN et al. : Synthesis of new metal-containing diols for polyurethanes Additionsreaktion als auch in bezug auf die S t r u k t u r Modellverbindungen der Additionspolymere dar. Bei einer ohne Nebenreaktionen ablaufenden Additionsreaktion ist ein bestimmter Mol(nx)u n d Masseanteil (wx) der einzelnen Oligomere a n der Prepolymermischung zu erwarten, der sich errechnet nach [5, 61: n, = P,rx -(1r)Z/(i + r ) wx = 0,5(1r)2rx -[P,(I + m ) + ( m -1)]/(m + r ) wobei m = Mb/M, u n d r = a/b fur 1 bzw. m = M,/Mb und r = b/a fur 2 sind.Die quantitative Auswertung der HPLC-Analysen (Tabelle 5) zeigt fur l a u n d 2a eine relativ gute Ubereinstimmung der berechneten Mol-bzw. Masseanteile m i t d e n aus den HPLC-Analysen experimentell ermittelten Werten. Damit ist die Bildung der regularen Prepolymere der jeweiligen Polymerisationsgrade in der erwarteten Quantit a t belegt, u n d Nebenreaktionen konnen hierbei ausgeschlossen werden.