PBMA, additives

The CYPHER stent employs two nonerodible polymers polyethylene-co-vinyl acetate (PEVA) and poly-n-butyl methacrylate (PBMA), The combination of sirolimus and these two polymers constitutes the basecoat formulation that is applied to a stent treated with paryleneC. In addition, a drug-free topcoat of PBMA polymer is applied to control the release kinetics of sirolimus (59), making this a diffusion-controlled reservoir device. The chemical structure of the polymers used in the CYPHER stent is shown in Figure 4,... 

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). 

Thus, this better fit may be solely due to the introduction of additional variables, however carefully utilized. The predicted NOEF behavior of C-l undergoing internal rotation superimposed upon overall isotropic motion is shown in Figure 1. Qualitatively, behavior such as that observed in PBMA can be interpreted in terms of crossovers arising from the mixing of overall motional components and rapid internal motional modes. The resulting NOEF values show complex field dependences. 

Cosolvents can enhance solubility of compounds in CO2, a topic beyond the scope of this chapter. It is useful, however, to point out some details on cosolvents in CO2. McHugh et al. demonstrate that a cosolvent can provide the specific interactions that are necessary to solubilize a compound in CO2 (70,71). For instance, butyl acrylate (BA) and ethyl hexyl acrylate (EHA) decrease the cloud point pressure of acrylate polymers owing to the specific polar interactions between the cosolvent with the acrylate backbone of the polymer (70). Addition of ethyl methacrylate (EMA) and butyl methacrylate (BMA) reduces the pressure needed to solubilize poly(ethyl methacrylate) (PEMA) and poly(butyl methacrylate) (PBMA) in CO2 (71). 

Addition of 10 wt% PPE turned the cylinders into spheres with PPE cores insulated by swollen PS blocks from a PBMA matrix. In PPE/P(S-b-BMA) 50/50 blends multilayer vesicles and lamellar structures coexisted. In blends having less than 5% of P(S-b-BMA), micelles with PBMA cores were observed in PPE matrix. 

It has been found that MMA/BMA copolymers and poly (methyl methacrylate) are compatible with poly (vinyl chloride). Poly(butyl methacrylate) on the other hand, is incompatible with PVC. Three component systems exhibit heterogeneous structures it seems that one phase consisted of the blend of PMMA with PVC, while the other was PBMA. Differences have been observed in the results of compatibility tests between the mixtures in the solid state and in solution. A solvent, an additional component, may bring about drastic changes in the behaviour of the system, as changes of interactions between polymers may then occur. 

Main polymer PES Copolymer additive PBMA-/>-PMAA-/)-... 

TABLE 3.2 Adhesion Strength of Steei Adhesive-Bonded Joints Using Adhesive Based on 40% Soiution of PBMA in MMA with Different Additives... 

The addition of surfactant to the adhesive changes the surface properties of the polymers, and consequently changes the wetting of the solid surface. As Fig. 5.1 shows, the addition of 1% OP-10 or of the fluorinated alcohol CF3(CF2)CH20H to an adhesive based on a 40% solution of PBMA in MMA decreases the interfadal angle for wetting of the steel siuface by the adhesive from 72° to 30-50°. 

Early examples using controlled radical polymerization were the synthesis of symmetric PMMA-PBMA-PMMA and PBMA-PMMA-PBMA by the sequential monomer addition route through ATRP. ... 

In addition, to improve adhesion between polymer matrix and HAp, several copolymer such as PMMA, PBMA, and PHEMA were grafted onto the surface of HAp using isocyanatoethyl methacrylate (ICEM) or hexamethylene diisocyanate (HMDI)/hydroxyethyl methacrylate (HEMA) [100]. These three methacrylate polymers were coupled to HAp particles via covalent bonding with isocyanate groups. 

Addition Polyurethanes Polyamide 6 Polyoxymethylene PMMA (polymethylmethacrylate) PBMA (polybutylmethacrylate) Acrylic copolymers Methacrylic copolymers Styrene copolymers Water-soluble polyamide... 

It is therefore evident that the experimental values of parameter %ab are closely related to the microstructure of a mixture. It has been demonstrated for the immiscible mixture of atactic PS and PMMA, for which the parameter Xab was determined by inverse gas chromatography and its microstructure from IR spectrum. It was found that in the composition range of20-40% PBMA, where Xab decreases, compared with other compositions, there is observed a redistribution of the rotational isomers of PS on addition of PBMA. The statistical weight... 

For an immiscible polyethylene-poly(butyl methacrylate) pair filled with fumed sihca, using NMR technique, the composition of the border layer was estabhshed (Table 7.1). As can be seen, with a growing filler content, the fraction of PBMA in the boundary layer increases and that of polyethylene decreases, i.e., the boundary layer is enriched by PBMA. Only 3% filler addition to the alloy, containing 75% polyethylene, results in small enrichment with this polymer, but above 10% filler the PBMA content increases. When considering the struc-... 

This product is different from the others described above because not only does it employ a different polymer blend, but it also uses a double polymer approach, where one polymer is used as a primer and the other as a drug reservoir. In this device, PBMA is used to enhance adherence and PVDF-HFP used to enhance drug binding. Additionally, no top coat is applied to the device. The polymer blend and the everoH-mus drug are mixed in the ratio of 83%/17% w/w polymer to drug, and subsequently this mixture is added to the PBMA coated stent. 

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