Functional initiator method

Recently, a functional initiator method has been reported for isobutene, where the initiator is CHsOQO)—Ar—C(CH3)2—Cl (Ar = t-BuC6H3) [156]. In the presence of TiCl4 (activator) and N,N-dimethylace-tamide (as an added nucleophile), the cumyl-type moiety of the initiator initiates living cationic polymerization the acetate moiety serves as the protected carboxylic acid. 

The polymerizable groups include methacryloyl, styrenic, epoxide, vinyl ether, and others, among which the methacryloyl-capped macromonomers are most widely available from vinyl ethers, styrene, and its derivatives. For example, the a-end methacryloyl group can be introduced by the functional initiator method, with the hydrogen halide-adduct of 2-... 

Functionalized poly(vinyl ether)s can be prepared by the functionalized initiator method by the use of a HI/I2 initiating system and a functionalized vinyl ether, resulting in a-functionalized polymers. Carboxylic add- and amine-terminated polymers were prepared by this method with high degrees of functionality as determined by H NMR. This method can be extended to the preparation of telechelic polymers by quenching the polymerization with the appropriate nucleophile. Methacrylate-functionalized poly(vinyl ether) s... 

This section concerns the synthesis of polyisobutylenes (PIB) bearing a Si-H head-group (HSi-PIB) by the use of Si-H containing functional initiator in conjunction with Me3Al coinitiator. First the effect of reaction conditions on the rate and molecular weight have been investigated and subsequently a H1 NMR method for the quantitative characterization of Si-H groups in HSi-PIB was developed. 

PS-fr-PBd) star-block copolymers were synthesized by the macromonomer technique in combination with anionic polymerization and ROMP [ 158], following the procedure outlined in Scheme 83. The macromonomers were prepared with two different methods. In the first the living diblock copolymer was reacted with ethylene oxide to reduce the nucleophihcity of the living end followed by termination with 5-carbonyl chloride bicycle (2.2.1) hept-2-ene, while in the second method the functional initiator 5-lithiomethyl bicycle... 

The ability to conduct radical reactions without the use of tin reagents is important. Allylic triflones have been used to conduct allylation reactions on a range of substrates (39) as a replacement for allyltributylstannane (Scheme 28). The main limitation was that unactivated or trisubstituted triflones failed to undergo reactions. In other nontin radical methods, arenesulfonyl halides have been used as functional initiators in the CuCl/4,4 -dinonyl-2, 2 -bipyridine-catalysed living atom-transfer polymerization of styrenes, methacrylates, and acrylates.The kinetics of initiation and propagation were examined with a range of substituted arylsulfonyl halides with initiator efficiency measured at 100%. 

Functional homopolymers can be synthesized by essentially two different methods. The first and more preferred way is to use a functional initiator which will ensure a high rate of chain end functionality. For instance, the polymerization of St initiated by a unimolecular terpyridine-functionalized nitroxide initiator yields well-defined PS homopolymers. The second technique is based on post-polymerization modifications. In this case, the reaction between mPEG and chloroterpyridine yields terpyridine-functionalized PEG building blocks, as illustrated in Scheme 13. 

The two anionic approaches (electrophilic termination and functional initiation) to the synthesis of these materials are discussed. The advantages of anionic methods are noted. Furthermore, the special benefits of the use of protected functional initiators and polymers are highlighted.Besides the usual advantages of the anionic methods, the protected functional initiator approach is a high yield and gel-free procedure that allows the attachment of reactive and/or mixed functionalities to polymer chain ends. 

The solution for a diffusion couple in which two semi-infinite ternary alloys are bonded initially at a planar interface is worked out in Exercise 6.1 by the same basic method. Because each component has step-function initial conditions, the solution is a sum of error-function solutions (see Section 4.2.2). Such diffusion couples are used widely in experimental studies of ternary diffusion. In Fig. 6.2 the diffusion profiles of Ni and Co are shown for a ternary diffusion couple fabricated by bonding together two Fe-Ni-Co alloys of differing compositions. The Ni, which was initially uniform throughout the couple, develops transient concentration gradients. This example of uphill diffusion results from interactions with the other components in the alloy. Coupling of the concentration profiles during diffusion in this ternary case illustrates the complexities that are present in multicomponent diffusion but absent from the binary case. 

The use of alkyllithium initiators which contain functional groups provides a versatile method for the preparation of end functionalized polymers and macromonomers. For a living anionic polymerization, each functionalized initiator molecule produces one macromolecule with the functional group from the initiator residue at one chain end and the active carbanionic propagating species at the other chain end. 

Most of the reported polyfvinyl ether) macromonomers have been prepared with a methacrylate end group which can be radically polymerized and which is non-reactive under cationic polymerization conditions [71-73]. Generally, the synthesis was based on the use of the functional initiator 30, which contains a methacrylate ester group and a function able to initiate the cationic polymerization of vinyl ethers. Such initiator can be obtained by the reaction of HI and the corresponding vinyl ether. With initiator 30 the polymerization of ethyl vinyl ether (EVE) was performed using I2 as an activator in toluene at -40 °C. The MW increased in direct proportion with conversion, and narrow MWD (Mw/Mn= 1.05-1.15) was obtained. The chain length could be controlled by the monomer to initiator feed ratio. Three poly(EVE) macromonomers of different length were prepared by this method Mn=1200,5400, and 9700 g mol-1. After complete... 

This review summarizes different synthetic methods of obtaining either molecular or maeromolecular fluorinated telechelic compounds. These compounds may be obtained either by direct synthesis or by syntheses which need many steps. Thus, reactions of polycondensation, polymerization, telomerization, fluorination of oligomers or the use of functional initiators are described in detail. On the other hand, the emphasis is also focussed on the interest of each method of preparation. Specific properties (solubility, thermal stability, surface properties. ..) of the obtained fluorinated telechelic products are discussed with regard to modern industrial requirements. We can observe that the compounds obtained by recently developed methods may be listed in two classes those which exhibit better surface properties and those which have better thermal stability. 

Concluding, based on these aspects, the laser initiation of explosives by laser diode radiation seems to be a very attractive and initiation method of the future. However, due to the limited power of laser diodes, the explosives might be thermally ignited and undergo a DDT, in contrast to the shock initiation which results by high-power solid-state laser radiation. The operating mode of laser diode initiators can be compared to that of electric hot-wires but with faster function times as has been demonstrated in the literature. 

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