Poly methyl -silane

Figure 3. UV Spectra for Poly(cyclohexyl-methy 1-co-iso-propyl-methyl silane) (50/50) with Different Molecular Heights.

Figure 14 Tacticity of (A) polypropylene and (B) poly(methyl-phenyl) silane.

B. Jambe, Ph.D. Thesis Thermal Behavior of Poly(methyl n-alkyl silane)s (Prom J. Devaux) Louvain-la-Neuve (1997). 

Multifunctional poly(dimethylsiloxane) (PDMS) networks were prepared via the addition of a silane hydrogen on poly(methyl-hydrogensiloxanes) (PMHS) to vinyl terminated linear PDMS... 

Figure 4.2 Comparison of UV absorption spectra of four optically active poly silanes in THF at 30°C poly methyl-(iS )-2-methylbutylsilane (1, a of 0.59), poly -hexyl-(5 )-4-methylpentyl-silane (2, a of 0.75), poly -hexyl-(5 )-3-methylpentylsilane (3, a of 0.92), and poly -hexyl-(5)-2-methyl-butylsilane (4, a of 1.25).

Figure 4.18 CD spectra of (a) poly[ methyl(methoxyphenyl)silane -co- (5 )-2-methylbutyl-(methoxyphenyl)silane ]s (30-32) and (b) poly[ -hexyl(methoxyphenyl)-silane -co- (5)-2-methylbutyl(methoxyphenyl)silane ]s (33 and 34) in THF at 20°C.

Figure 4.19 UV, CD, and FL spectra of (a) poly methyl(ra-( )-2-methylbutoxyphenyl)silane (38) and (b) poly methyl(/ -(S)-2-methylbutoxyphenyl)silane (39) in THF at 23-25°C.

Figure 4.20 29Si-NMR spectra of poly[methyl((J>)-2-methylbutoxyphenyl)silane]s (38 and 39) in benzene-Jg at 50°C.

A series of optically active poly alkyl(phenyl)silane derivative copolymers with different chiral molar composition 44 and 45, are shown in Chart 4.7, along with homopolymers poly(methyl(phenyl)silane) (42) and poly(n-hexyl(m-tolyl)silane) (43). 

Avseenko et al. (2001) immobilized antigens onto aluminum-coated Mylar films by electrospray (ES) deposition. Various surface modifications of the metallized films were studied to determine their abilities to enhance sensitivity. The plastic surfaces were firsf cleaned by plasma discharge treatment, followed by coating with proteins (BSA and casein) or polymers such as poly (methyl methacrylate) or oxidized dextran, or they were exposed to dichlorodimethyl silane to create hydrophobic surfaces. Protein antigen was prepared in 10-fold excess sucrose and sprayed onto the surfaces to form arrays with spot diameters between 7 and 15 pm containing 1 to 4 pg protein. 

Table II. Solvent Effect on Yields of Poly (Cyclohexyl Methyl) Silane.

An array of 10- i,m microlenses was fabricated from the adhesion of an aminated silicasol on a poly[methyl(phenyl)silane-co-methyl(3,3,3-tri-fluoropropyl)silane] (CF3PMPS) film patterned by UV light irradiation.132 By soaking the UV-patterned polysilane film into the sol-gel solution, a convex xerogel layer adhered only to the UV-exposed poly silane, which was cured to form a glass that functioned as a condensing lens. 

A powerful technique for investigating these different species is 29Si-NMR (see Fig. 8.1). Different lines can be observed in the 29Si-NMR spectrum of a silicate solution corresponding to the differently positioned 29Si nuclei in the (poly)sili-cate ions. The highest values for the chemical shift (8 = -71.5 ppm with respect to tetra methyl silane) are found for the monomeric silicate units while the resonances of fully condensed silicon atoms (i.e. Si-(0-Si)4 tetrasiloxy silane) are to be found at the lowest values for the chemical shift (8 = -110 ppm). 

To our knowledge, only one study describes the synthesis of block copolymers from the cleavage of the Si-Si bond of silanes [240], Poly(methyl phenyl silane) s 61 appear as efficient photoinitiators for the free radical polymerization of MMA leading, after short irradiation time, to PMMA 63 which reaches molecular weights of 54 000. These silylated PMMAs produce block copolymers 64 in... 

Catalysis of the synthesis of benzoic anhydride and the hydrolysis of benzoyl chloride, diphenyl phosphorochloridate (DPPC), and benzoic isobutyric anhydride in dichloromethane-water suspensions by water-insoluble silanes and siloxanes, 3- and 4-trimethylsilylpyridine 1-oxide (3b and 3c, respectively), 1,3-bis(l-oxypyridin-3-yl)-l,1,3,3-tetramethyldisiloxane (4), and poly[methyl(l-oxypyridin-3-yl)-siloxane] (5) was compared with catalysis in the same systems by water-soluble pyridine 1-oxide (3a) and poly(4-vinylpyridine 1-oxide) (6). All catalysts were effective for anhydride synthesis and promoted the disproportionation of benzoic isobutyric anhydride. Hydrolysis of benzoyl chloride gave benzoic anhydride in high yield ( 80%) for all catalysts except 3a, which gave mixtures of anhydride (52%) and benzoic acid (39%). The order of catalytic activity for DPPC hydrolysis was 5 > 4 > 3b > 3a > 3c > 6. The results suggest that hydrophobic binding between catalyst and lipophilic substrate plays an important role in these processes. 

The poly(methyl methacrylate)s prepared in this experiment, as well as polymers formed in model reactions with silanes that contain bulky substituents (such as phenyldimethyl and diphenylmethyl groups), have predominantly syndiotactic structures identical to polymers prepared by the conventional group-transfer process. This result supports a two-step dissociative mechanism for a group-transfer process, because steric hindrance from bulky silyl groups should increase the proportion of isotactic triads in the hypothetical associative concerted propagation step. 

Photoablation of Copolymers, Other workers have also investigated the phenomenon of polysilane self-development. Zeigler and co-workers (13) have studied the self-development of a number of polysilane homo- and copolymers and found that self-development eflSciencies increase with the size of substituents. They also suggested that the material removal process for alkyl-substituted poly silanes at low fluences (<50 mj/cm per pulse) is predominantly photochemical rather than photothermal. By using a 1 1 copolymer, poly(methyl-n-propylsilane-co-isopropylmethylsilane), images were generated by excimer laser exposure at 248 nm. 

To study the structural sensitivity of poly silanes to ionizing radiation, a number of samples were irradiated with a calibrated Co source, and the degraded materials were analyzed by GPC in a manner similar to that described for the determination of photochemical quantum yields (59). In radiation processes, the slopes of the plots of molecular weight versus absorbed dose yield the G values for scissioning, G(s), and cross-linking, G(x), rather than the respective quantum yields. These values, which represent the number of chain breaks or cross-links per 100 eV of absorbed dose, are indicative of the relative radiation sensitivity of the material. The data for a number of polysilanes are given in Table IV. Also included in Table IV for comparison is the value for a commercial sample of poly(methyl methacrylate) run under the same conditions. The G(s) value of this sample compares favorably with that reported in the literature (83). 

Figure 11. Screw-sense-selective photolytic cleavage of the M-helical segments in poly[methyl(2-methylbutyl)-silane] and subsequent Wurtz coupling of P-helical segments. (Reprinted with permission from ref 127. Copyright 1994 American Chemical Society.)...

Auxiliary agents poly (methyl siloxane) and glycidoxy-propyltrimethoxy silane ... 

Figure 2.17 NMR spectra of poly(methyl methacrylate) (15% solution in chloroform, r = tetramethyl silane reference peak). (a) Mainly syndiotactic (b) mainly isotactic. The methyl ester group appears at 6.40t in both spectra and is unchanged by chain configuration. (From Ref. 17.)...

---