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SIBS polymer

The discovery of living cationic polymerization has provided methods and technology for the synthesis of useful block copolymers, especially those based on elastomeric polyisobutylene (Kennedy and Puskas, 2004). It is noteworthy that isobutylene can only be polymerized by a cationic mechanism. One of the most useful thermoplastic elastomers prepared by cationic polymerization is the polystyrene-f -polyisobutylene-(>-polystyrene (SIBS) triblock copolymer. This polymer imbibed with anti-inflammatory dmgs was one of the first polymers used to coat metal stents as a treatment for blocked arteries (Sipos et al., 2005). The SIBS polymers possess an oxidatively stable, elastomeric polyisobutylene center block and exhibit the critical enabling properties for this application including processing, vascular compatibility, and biostability (Faust, 2012). As illustrated below, SIBS polymers can be prepared by sequential monomer addition using a difunctional initiator with titanium tetrachloride in a mixed solvent (methylene chloride/methylcyclohexane) at low temperature (-70 to -90°C) in the presence of a proton trap (2,6-dt-f-butylpyridine). To prevent formation of coupled products formed by intermolecular alkylation, the polymerization is terminated prior to complete consumption of styrene. These SIBS polymers exhibit tensile properties essentially the same as those of... [Pg.97]

Positive, secondary ion mass spectra of SIBS polymer containing taxol recorded using Ga+ ions and Ceo ions under static conditions are shown in Figure 46.23. The (M -1- H) ion from taxol is not observed while the contribution of polydimethyl siloxane (PDMS), which is innate to the polymer formulation, is quite significant with Ga+ ions. The molecular ions of taxol and higher mass fragments are enhanced using Ceo primary ions. [Pg.1131]

FIGURE 46.23 Positive, secondary ion mass spectra of SIBS polymer containing paclitaxel (PTx). Data were recorded using Ga ions (lower spectrum) and Ceo ions (upper spectrum) under static conditions. [Pg.1131]

FIGURE 46.24 Depth profile of SIBS polymer containing PTx. Secondary ion intensities for select species plotted as a function of primary ion (Cso ) dose. [Pg.1132]

Consequently, it is reasonable to assess that there is an enrichment of PDMS and taxol at the surface of the SIBS polymer, although, it is not possible to quantitate these findings. [Pg.1132]

Loss of catalytic complex by dissolution from the support This can either occur to physically bound catalysts (physisorbed, entangled in a polymer, hydro-gen-bonded), when the reaction medium has too-good solvent properties. The catalyst complex can also be dissolved from ionically bound species by ion exchange with electrolytes in the reaction mixture, or when the covalent bond to the support is broken (e.g., by hydrolysis). In the case of SIB catalysts, a good solvent such as ethanol can displace a salen-type ligand from the metal. [Pg.1461]

The TAXUS DES utilizes the Translute polymer—a matrix-controlled system made of a soft elastomeric triblock co-polymer, poly(styrene-b-isobutylene-b-styrene) (SIBS) (37). The chemical structure of SIBS is shown in Figure 6. [Pg.273]

See color plate) Atomic force microscopy images and drug release kinetics of the paclitaxel-poly(styrene-i>isobutylene-i>styrene) polymer combination. Abbreviations PTx, paclitaxel SIBS, poly(styrene-b-isobutylene-b-slyrene). [Pg.275]

Biostable polymers have been chosen for use in the majority of DES that are marketed or in clinical development. The main attractiveness of biostable polymers is their physical stability, inertness toward the drug, and predictable drug kinetics. In Cypher, a blend of poly(ethylene-co-butyl methacrylate) (PEVAc/PBMA) is used as the drug carrier. This hydrophobic polymer, along with additional polymer process steps, effectively controls the release of sirolimus, eluting 80% of the drug over 30 days after implantation. In the case of Taxus, atri-block copolymer of styrene-isobutylene-styrene (SIBS) is used as the hydrophobic polymer matrix that releases 10% of incorporated paclitaxel in the first 30 days (20). [Pg.291]

Polymer matrix PEVAc/PBMA blend SIBS Block PC-Copolymer PC Copolymer topcoat PLGA... [Pg.294]

As outlined in the previous section, the good charge storage of the binary PPE/PS blends was in part attributed to the proposed presence of heterogeneities in the polymer bulk. In this section, heterogeneities are further introduced by adding a third component, namely the triblockcopolymer poly(styrene-Msobutylene-fe-styrene) (SIBS) to form ternary polymer blends with PPE and PS [65], The chemical struc-... [Pg.187]

Silicon-29 NMR has been used to determine chain and block lengths in siloxane oligomers and polymers. The chemical shifts of chain or block terminal silicon atoms differ substantially from the chemical shifts of the silicon atoms in the middle of the siloxane chain (or block, as in a block copolymer)130 -134. Thus by integrating the areas under the resonances for SiA and SiB the average degree of polymerization (DP) for disiloxanols, for example, can be determined131 from equation 6 ... [Pg.547]

Ranade et al. [33] describe the paclitaxel-eluting coronary stent, including the methodology to characterise drug delivery from this stent. The polymer chosen for this stent was poly (styrene-P-isobutylene- P-styrene) (SIBS shown in Figure 13) and showed good mechanical properties and stent performance. [Pg.681]

Further research has continued into the development of drug eluting coronary stents for the treatment of cardiovascular restenosis. Because the miscibility of paclitaxel with SIBS as demonstrated by the previous authors [33] is low as measured by DSC, Sipos et al. [34] have reported on the synthesis of poly (p-tertbutyldimethylsiloxy)styrene (TBDMS)-P-isobutylene (IB)-PTBDMS), which can be hydrolysed to poly(PHOS-P-PIB-P-PHOS) in order to modulate the solubility of PTx in the polymer, which, in turn, affects its release from the polymer. Further chemical modification of the polymer can be undertaken to effect changes in the polarity of the polymer, including acetylation, which gives rise to PAcOS-P-PIB-p-PAcOS. [Pg.682]

Polycarboranesiloxane (SiB) n. A polymer whose chain consists of alternating carbo-nane and siloxane groups. Commercial resins contain active end groups that may be vulcanized with peroxides to yield rubbers resistant to high temperatures (260°C in air). [Pg.743]

The basic concept to use block co-polymer for the application to the DMFC is that ordered hydrophilic/hydrophobic phase separations offer a route for the selective transport of proton ions with reduced methanol crossover in the hydrophilic domains, because block co-polymers can be selectively sulfonated using post-sulfonation methods, and the block co-polymers can be verified over a wide range of structures during anionic polymerization. For example, methanol transport behaviors of a triblock co-polymer ionomer, sulfonated poly(styrene-isobutylene-styrene) (S-SIBS), were compared with Nafion to determine whether the sulfonated block co-polymer could serve as a viable alternative membrane for application to the DMFC [62]. The S-SIBS membranes showed approximately 5-10 times more methanol selectivity than that of Nafionll , although the S-SIBS membranes exhibited low conductivity compared with Nafion 117. [Pg.326]

PEVA poly(ethylene-co-vinyl acetate), PBMA poly(n-butyl methacrylate), SIBS poly(styrene-b-isobutylene-b-styrene) block copolymer, PC phosphorylcholine pol5rmer, PVDF-HFP poly(vinyUdene fluoride)-hexafluoropropylene, BioLinx hydrophobic Cio-polymer/hydrophilic Ci9-polymer/poly(vinylpyrrolidone) (PVP), PLA polylactide... [Pg.444]

Cell adhesion. For most applications the adhesion of cells is of fnndamental interest being the initial event of cell attachment. A simple method to quantify adherent cells is to incnbate cells over a snrface for a period of time snbsequently followed by the detachment of loosely adherent cells by gently washing the surface. Remaining cells can be labeled by flnorescent dyes and quantihed using flnorescent measnrements. Cell adhesion assays are also freqnently used to assess monocyte or platelet adhesion on polymeric snrfaces [215, 216]. In this context Hezi-Yamit et al. [217] did show that polymer hydrophilicity should be considered as a parameter to assess the biocompatibility of polymer surfaces. They showed that hydrophobic polymers such as PBMA or SIBS promote the adhesion of inflammatory activated monocytes while more hydrophilic polymers (e.g. PC (Phosphorylcholine) polymer) lead to less pro-inflammatory responses. [Pg.459]

In Europe, new regulations defined in ZTV-SIB (Additional Technical Contract Conditions and Regulations for the Protection and Restoration of Concrete Building Components) specify crack-bridging at -20 °C [88]. As a result, lower Tg polymer systems have been developed, which yield membrane flexibiHty and hairline crack... [Pg.244]


See other pages where SIBS polymer is mentioned: [Pg.273]    [Pg.675]    [Pg.177]    [Pg.407]    [Pg.273]    [Pg.675]    [Pg.177]    [Pg.407]    [Pg.193]    [Pg.204]    [Pg.557]    [Pg.558]    [Pg.22]    [Pg.292]    [Pg.204]    [Pg.175]    [Pg.176]    [Pg.3]    [Pg.574]    [Pg.682]    [Pg.639]    [Pg.1507]    [Pg.120]    [Pg.975]    [Pg.120]    [Pg.436]    [Pg.449]    [Pg.83]   
See also in sourсe #XX -- [ Pg.97 ]




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