Polyisobutylenes technique

Though living anionic polymerization is the most widely used technique for synthesizing many commercially available TPEs based on styrenic block copolymers, living carbocationic polymerization has also been developed in recent years for such purposes [10,11], Polyisobutylene (PlB)-based TPEs, one of the most recently developed classes, are synthesized by living carbocationic polymerization with sequential monomer addition and consists of two basic steps [10] as follows ... 

Another study looked at the miscibihty of E-plastomer-polyisobutylene blends. Blends were prepared from linear E-plastomers and a polyisobutylenes in the entire composition range. Flory-Huggins interaction parameters were determined from DMTA and DSC measurements. The usual technique had to be modified in the case of DSC data, since the Tg of E-plastomers cannot be detected by this technique. The two methods yielded identical results and indicated good interaction of the components, which was supported also by a SEM study and the mechanical properties of the blends. 

It is used in industry for preparing Polyacrylonitrile by free radical polymerisation and polyisobutylene by cationic polymerisation. Block copolymers are prepared exclusively by this technique. 

The inifer technique is a most convenient route for the preparation of well-defined end-reactive polyisobutylenes (PIB)(1). These materials may be linear or three-arm star telechelics carrying exactly 2.0 or 3.0 end-functions, respectively. The inifer technique yields tert.-chlorine-telechelic product, for example,... 

Table I. Comparison of Semicontinuous and Conventional Polymerization Techniques for the Preparation of Telechelic Polyisobutylenes by Binifer and Trinifer...

Table II. Comparison between Conventional Batch and Semicontinuous Inifer Techniques for the Preparation of End-Reactive Polyisobutylenes...

The measurement technique was the crux of a paper by Acha et al.27 discussing the process of the dechlorination of aliphatic hydrocarbons. An ATR-FTIR sensor was developed to monitor parts per million (ppm) of trichloroethylene (TCE), tetrachloroethylene (PCE), and carbon tetrachloride (CT) in the aqueous effluent of a fixed-bed dechlorinating bioreactor. It was found that the best extracting polymer was polyisobutylene (PIB) as a 5.8 pm film. This afforded detection limits of 2, 3, and 2.5 mg/1 for TCE, PCE, and CT, respectively. The construction and operation of the measurement system are detailed in the paper. 

Figure 10 shows a spectrum of butyl rubber gum stock obtained on the solid at 80°C using normal pulsed FT techniques. Clearly it could be identified as a component in fabricated materials by direct nmr spectral analysis. Figure 11 shows spectra obtained from various portions of typical rubber products. These samples were cut from the rubber product, placed in an nmr tube without solvent, and spectra obtained at an elevated temperature. The data show how polyisoprene, a polyisoprene/polybutadiene blend and a polyisobutylene/polyisoprene/polybutadiene rubber blend are quickly identified in the materials. Figure 11a shows processing oil was present, and which was confirmed by solvent extraction. 

The Inifer Method. A special case of controlled initiation is the inifer method (17). The word inifer (from initiator trans/t / agents) describes compounds that function simultaneously as initiators and as chain-transfer agents. Chain transfer to inifer regenerates R+. The inifer technique provided the first carbocationic route toward the synthesis of telechelic (a,G) functional) polyisobutylenes and more recendy telechelic poly( >-chlorostyrenes) (18). To prepare telechelic products chain transfer to monomer must be absent, and with BC13 as coinitiator this requirement is fulfilled. 

The question immediately raised is would this technique portray an opposite or negative adhesion response if applied to a polymer blended system where no interfacial bonding could be present Such a system would be cis-polybutadiene and high molecular weight polyisobutylene restricted to that portion of the blend system where polyisobutylene is the minor dispersed phase in cis-polybutadiene. A high molecular weight polyisobutylene [L-300 Vistanex (Enjay Chemical Co.)] was compounded with zinc oxide, sulfur, and TMTDS and then dissolved in hexane. cis-Polybutadiene (Phillips Chemical Co.) was also mixed with... 

This technique seems to have been introduced in late 1998, and consists of extracting organic contaminants from the soil with a solvent, generally sub-critical water, and then passing the extract through a small disc of solid sorbent. The solid sorbents discussed to date include graphitised carbon black [123], styrene-divinyl benzene [124],Carbograph-4 [122] and polyisobutylene [193]. 

Butyl Rubber. Butyl rubber is used in conjunction with other thermoplastic hydrocarbon rubbers (for example, polyisobutylene) to make pressure-sensitive hot-melt adhesives. Such formulations include also tackifying resins and oils. Adhesives of low viscosity are produced, and these may be applied by the hot-melt spray technique (see page 106). 

The terminally bifunctional prepolymer, carboxy-terminated polyisobutylene, is prepared by the pyridine-modified ozonization of a copolymer of piperylene (2-4% ) and isobutylene. Figure 1 shows a block diagram of the process. The high molecular weight elastomer can be prepared by the conventional techniques of isobutylene-diene copoly-... 

New Products Prepared by the Inifer Technique. A new family of linear and three-arm star polyisobutylenes have been prepared by the inifer technique. The inifer systems used were cumyl chloride (minifer) p-dicumyl chloride (binifer) and sym-tricumyl chloride (trinifer) always in combination with BCI3 coinitiator (1) ... 

This paper concerns the synthesis of a new telechelic polyisobutylene diol, a, a)-di (hydroxy) po lyi so-butylene (formula IV in Scheme I), and the preparation of new linear polyurethanes containing polyisobutylene (PIB) soft segments by the use of this diol and conv-ventional extension techniques with TDI. 

B. Techniques. The synthesis and purification of a, u)-di (tejrt.-chloro ) poly isobutylene C1-PIB-C1 (formula I in Scheme I) and the preparation of ct, io-di ( isobut-enyl)polyisobutylene (formula II in Scheme I) by quantitative regioselective dehydrochlorination of Cl-PIB-C1 have been described [1,3]. Details of the synthesis of a, u-di (hydroxy)polyisobutylenes HO-CH2-PIB-CH2-OH (formula IV in Scheme I) by hydroborations of ct,w-di-( isobutenyl)polyisobutylene with 9-BBN or BH3 THF, have been given elsewhere [4]. 

In conclusion, these experiments indicate the possibility of synthesizing polyurethanes with polyisobutylene soft segments. The polyisobutylene diols have been synthesized by the inifer method and careful characterization techniques indicate Fn = 2.0. It is anticipated that polyurethanes with polyisobutylene soft segments will exhibit superior thermal, UV, oxidative and chemical resistance to conventional polyurethanes having polyester, polyether, or polybutadiene soft segments. 

Inifer Technique. Inifers are bifunctional initiator-chain transfer agents that have been used for the preparation of a,w-difunctional polyisobutylene carrying—CH9C(CH.3)9C1 end groups (10, 1, 166-168). 

Heterogeneous Graft Copolymerization. Poly(vinyl chloride) films and powders (183) and chlorinated polypropylene (184) fibers were grafted with styrene, isobutylene, and styrene, respectively. Grafting from techniques were used. By using the same technique a silica surface first treated with chlorosilyl functional groups was grafted with polyIsobutylene and butyl rubber (185. 186) ... 

This is accomplished by translation of the small curves along the log t axis until they are all superimposed to form a large composite curve. The technique can be illustrated using data for polyisobutylene at several temperatures. An arbitrary temperature To is first ehosen to serve as a reference, which in the present case is 298 K. 

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