Copolymers silane synthesis

Gross-Linking. A variety of PE resins, after their synthesis, can be modified by cross-linking with peroxides, hydrolysis of silane-grafted polymers, ionic bonding of chain carboxyl groups (ionomers), chlorination, graft copolymerization, hydrolysis of vinyl acetate copolymers, and other reactions. 

See also PBT degradation structure and properties of, 44-46 synthesis of, 106, 191 Polycaprolactam (PCA), 530, 541 Poly(e-caprolactone) (CAPA, PCL), 28, 42, 86. See also PCL degradation OH-terminated, 98-99 Polycaprolactones, 213 Poly(carbo[dimethyl]silane)s, 450, 451 Polycarbonate glycols, 207 Polycarbonate-polysulfone block copolymer, 360 Polycarbonates, 213 chemical structure of, 5 Polycarbosilanes, 450-456 Poly(chlorocarbosilanes), 454 Polycondensations, 57, 100 Poly(l,4-cyclohexylenedimethylene terephthalate) (PCT), 25 Polydimethyl siloxanes, 4 Poly(dioxanone) (PDO), 27 Poly (4,4 -dipheny lpheny lpho sphine oxide) (PAPO), 347 Polydispersity, 57 Polydispersity index, 444 Poly(D-lactic acid) (PDLA), 41 Poly(DL-lactic acid) (PDLLA), 42 Polyester amides, 18 Polyester-based networks, 58-60 Polyester carbonates, 18 Polyester-ether block copolymers, 20 Polyester-ethers, 26... 

Hydrosilation reactions have been one of the earlier techniques utilized in the preparation of siloxane containing block copolymers 22,23). A major application of this method has been in the synthesis of polysiloxane-poly(alkylene oxide) block copolymers 23), which find extensive applications as emulsifiers and stabilizers, especially in the urethane foam formulations 23-43). These types of reactions are conducted between silane (Si H) terminated siloxane oligomers and olefinically terminated poly-(alkylene oxide) oligomers. Consequently the resulting system contains (Si—C) linkages between different segments. Earlier developments in the field have been reviewed 22, 23,43> Recently hydrosilation reactions have been used effectively by Ringsdorf 255) and Finkelmann 256) for the synthesis of various novel thermoplastic liquid crystalline copolymers where siloxanes have been utilized as flexible spacers. Introduction of flexible siloxanes also improved the processibility of these materials. 

The synthesis of PDMS macromonomers with vinyl silane end-groups and their free-radical copolymerization with vinyl acetate, leading to poly(vinyl acetate)-PDMS graft copolymers, was described 346). The copolymers produced were later hydrolyzed to obtain poly(vinyl alcohol)-PDMS graft copolymers. 

A new convenient polymer modification for the conversion of the Si—H to Si—OH by the selective oxidation of the Si—H bond by dimethyldioxirane has been described. The oxyfunctionalization of the silane precursor polymers proceeded rapidly and quantitatively and can be applied to the synthesis of a wide variety of novel silanol polymers with specific properties from the corresponding precursor polymers containing Si—H functional groups. Control over the properties of these silanol polymers, such as reactivity and self-association of silanols, was realized through the placement of different substitute groups bonded directly to the silicon atom and by the variation of silanol composition in a copolymer. These novel silanol polymers with a... 

As an alternative to condensation of dichlorosilanes by alkali metals, it is possible to synthesize poly silanes by the reaction of preformed dilithio compounds with dichlorosilanes. An early synthesis of a copolymer by this route is illustrated in equation (19).10 (see also Section 5.9.2). Finally, poly(phenylmethylsilylene) has been made by thermal decomposition of a silyl-mercury polymer36 (equation (20)). 

The synthetic procedure for the synthesis of the inverse starblock copolymers is given in Scheme 25. Diblock arms (I) having the living end at the PS chain end were prepared by anionic polymerization with sequential addition of monomers. In order to accelerate the crossover reaction from the PILi to the PSLi chain end a small quantity of THF was added prior the addition of styrene. The living diblock (I) solution was added dropwise to a stoichiometric amount of SiCl4 until two arms are linked to the silane. This step was monitored by SEC and is similar to a titration process. The end point of the titration was determined by the appearance of a small quantity ( 1%) of trimer in the SEC trace. The diblock (I) was selected over the diblock (II) due to the increased steric hindrance of the styryl anion over the isoprenyl anion, which makes easier the control of the incorporation of only two arms into the silane. 

SCHEME 4. Electrochemical synthesis of a silane-germane copolymer with a —Si—Ge—Si-sequence... 

Synthesis of carboorganosiloxane copolymers and polymers is based on hydride polyaddition of organohydrosiloxanes to organoalkenyl silanes [69], Recently, this reaction is of great interest in the field of obtaining complex monomers [70], as well as in the field of study of addition mechanisms on various Pt, Pd, Co and metal carbonyl catalysts [71-74] and specificity of actions of one or other catalytic systems [75], Besides carboorganosiloxane oligomers and linear polymers, other compo-unds were also synthesized by this method [76 -78],... 

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... 

A magnesium sacrificial anode is also effective for the synthesis of Si-Ge and Ge-Ge bonds. This method is quite successful for the preparation of polygermanes and germane-silane copolymers [Eq. (49)] [183]. Polygermanes were also prepared by conventional electrochemical reduction of dihalogermanes using a Pt cathode and an Ag anode [184]. 

Propyl trimethoxysilane 4a exhibits a much lower reaction rate than that of trimethoxy vinyl silane 4b. This is the result of a reduced electron density at the silicon atom in 4a compared to 4b bearing the vinyl groiq). In contrast, the high reactivity in die case of 5, the saturated counterpart of 3a, is not only retained, but enhanced. This can be explained by a more effective electron transfer from the ester moiety to silicon in the case of 5 compared to 3a due to the missing electron delocalization. The high hydrolysis speed found for compound 5 indicates that the high reactivity of 3a can be transferred into a polymer in the case of a copolymer synthesis. 

The usual synthesis of polysilanes is by Wurtz-type condensation of diorganodichloro-silanes with finely-divided sodium metal in an inert diluent. Either homopolymers or copolymers can be made (equation 44). The organic groups can be widely varied, to... 

The standard method for synthesis of poly silanes follows the original preparation of (Me2Si) by Burkhard. Diorganodichlorosilanes are treated with finely dispersed sodium metal in an inert diluent, usually above the melting point of sodium. Homopolymers are obtained from single dichlorosUanes, whUe cocondensation of mixtures of dichlorosilanes yields copolymers (equation 33). Toluene is the most commonly used solvent, but other aliphatic or aromatic solvents are also effective. After completion of the reaction, the mixture is quenched with alcohol and/or water to destroy any excess sodium and silyl anion, then filtered and... 

A similar approach was used to construct a unique triblock copolymer having dendritic termini connected by linear segment. The synthesis of the dendritic-fe/oc/c-linear-fetocA -dendritic PS, referred to as the pom-pom structure due to its dumbbell-like shape, results from a convergent anionic polymerization procedure using dichlorodimethyl-silane as a coupling agent [119]. 

---