Polysiloxanes aldehydes

A blend of a polyoxyalkylene-polysiloxane copolymer and an alkoxy-lated phenol-aldehyde resin is useful as a demulsifier [1457, 1458]. 

The polyoxyalkylene units in the copolymer have a molecular weight below 500, and the polysiloxane units have 3 to 50 silicon atoms. The resin has a phenol/aldehyde ratio of 2 1 to 1 5 and an average molecular weight of 500 to 20,000 Dalton. The composition shows synergistic demulsification activity when compared with the individual components. The siloxane units can be either in blocks [979,980] of the polyoxyalkylene-polysiloxane copolymer or randomly distributed [728,729]. 

Abstract Aldehyde functional polysiloxanes (1) (Fig. 1) can be selectively prepared in high yield and purity by oxidation of the corresponding carbinols with technical bleach and catalytic amounts of TEMPO. This simple oxidation method is also successfully used for the preparation of the corresponding carboxylic acids 2 (Fig. 1). The stability, reactivity and chemical properties of new compounds 1 and 2 are investigated. 

Aldehyde functionalities are very reactive toward amino and hydroxy groups. As a result, polymers 1 can bind to cellnlose or protein snrfaces. Their reactivity toward nucleophiles enables them to take part in varions crosshnking reactions, e.g. with amines. Carboxy fnnctional polysiloxanes 2 are also able to bind to surfaces because of the carboxy group s high polarity. They can nndergo crosslinking reactions, e.g. with epoxides. Their salts are good snrfactants. 

To date, three methods have been described for the synthesis of aldehyde functional polysiloxanes (1) in patent literature, but these are not practiced. The hydroformylation of olefinic siloxanes with carbon monoxide and hydrogen under high pressure and temperature conditions is possible (Scheme 1, eq. (1)), but produces a mixture of... 

Scheme 1 Methods for the synthesis of aldehyde functional polysiloxanes described in the literature [1-5] (1) hydroformylation, (2) and (3) ozonolysis, (4) hydrosilylation of acrolein acetals and acid hydrolysis...

Concern about redistribution reactions of the polysiloxane backbone and the formation of small amount of aldehyde-functional polysiloxane as side-product led the authors to explore several acid catalysts with the lowest moisture content possible, with activated clay being finally preferred. Size-exclusion chromatography was performed on some of the resulting polysiloxanes. 

A vast majority of the commercially available silicon-containing polymers today are polysiloxanes or silicones. In the same way that aldehydes and alcohols are characterized by the presence of the -CHO-H and = C-OH moieties, respectively, a siloxane is a compound containing the bond =Si-0-Si=, and silicones are materials consisting of alternating silicon and oxygen atoms in which most silicon atoms are bound to at least one monofunctional organic radical. Polymers and copolymers of R, R2, and R3 monomers are termed poly(siloxanes). Linear poly(siloxanes)... 

Fig. 11 Different compounds are formed when APTES or TESBA react with water (a) polysiloxanes produced between silicon and oxygen bonds, (b) alcohols produced between water and alkyloxy- ends or alcohols produced between water and the TESBA aldehyde end, and (c) nitrogen oxides produced between water and the APTES amine end...

PDM-0421, PDM-0821, PDM-1922. See Phenylmethyl polysiloxane PDM-704, PDM-7050. See Tetramethyl tetraphenyl trisiloxane PDMS. See Polydimethylsiloxane PDX-84367. See Polyetherimide resin PDX-84368. See Polycarbonate PDX-84369. See Polybutylene terephthalate PE-25. See Polyethylene, medium density PE. See Pentaerythritol Polyethylene PEA P-PEA. See Phenethyl alcohol Peach aldehyde. See y-Undecalactone Peach kernel extract. See Peach (Prunus persica) kernel extract... 

Radical addition of thiol or thiol-modified support to the vinyl group gives the respective thioether linkage 34 and represents one of the most convenient ways to immobilize Cinchona alkaloids [163, 172]. There are also few examples of platinum-catalyzed hydrosilylation of Cinchona alkaloids toward 11-silyl-substituted derivatives 35 with the use of monomeric silanes or polysiloxane polymers [173-175]. De Vries reported rhodium-catalyzed hydroformylation of the four main members of Cinchona alkaloids carried out on a hundred gram scale. Under optimized condition, linear aldehydes 36 were selectively obtained with the yield over 80% [176]. 

Polysiloxanes with terminal hexenyl groups were converted by ozonol-ysis into polysiloxanes with terminal aldehyde functionality. These were used in combination with copper octanoate, triethylamine, pyridine and triphenylphosphine to initiate the polymerization of styrene, methyl methacrylate and styrene/methyl methacrylate mixtures at 70°C. The polymerizations yielded block copolymers containing polysiloxane and vinyl (co)polymer segments. Depending on how the polymerizations terminated, the block copolymers had triblock or multiblock architectures. 

Aldehyde-Functional Polysiloxane Synthesis. Poly (dimethylsiloxanes) containing 1-hexenyl-dimethylsiloxane end groups, DC 7691 (n = 200), DC 7692 (n = 100) and DC 7697 (n = 30), were dissolved in hexane or methylene chloride (1 g/ml) and the solutions were cooled to -20°C. Ozone was then bubbled through the solutions and then into a Nal solution to decompose any excess that had not been reacted and prevent its release to the atmosphere. Treatment of the reaction mixtures with ozone was stopped after the Nal solution developed a blue color indicating that all the unsaturation had been consumed. The reaction mixtures were then allowed to warm to room temperature and heated for one hour at 40 C with Zn powder/acetic acid (1 1 molar ratio) to convert the ozonized groups on the polymers to aldehyde groups. 

The reaction mixtures were then filtered to remove zinc oxide, washed with water to remove excess acetic acid and then dried. Removal of the solvent by distillation then yielded the aldehyde-functional polysiloxanes. Listed below are the polymers prepared for use in this study. The polymers exhibited characteristic aldehyde absorption at- 1733 cm . ... 

General Chemistry. Although polysiloxanes that bear aldehyde functionality have not been described previously, they can be prepared quite easily by ozonolysis of precursors that bear terminal olefmic groups. Hydrosilation can be used to prepare such materials from readily available precursors. The following series of reactions was thus used to prepare polysiloxanes with terminal aldehyde functionality. 

Reaction of ozonized polysiloxanes with zinc and acetic acid at 40° converts the ozonide groups to aldehyde groups. Table I provides information about the aldehyde-functional polysiloxanes that were employed in this investigation. 

When solutions of aldehyde-functional polysiloxanes, copper octanoate, trieth-ylamine, pyridine, triphenylphosphine and monomer in inert solvents such as benzene are heated, radicals can be generated at the polysiloxane ends and these can initiate polymerization. This is shown below, where M is a monomer unit. 

This equation is based on the assumption that there are as many polystyrene segments in the copolymer as polysiloxane segments which, in turn, is based on the assumptions that each aldehyde group in the parent polysiloxane yields a radical and that termination occurs exclusively by radical combination. 

Such structures are believed to result from termination of growing polystyrene segment radicals by combination. Each such termination reaction yields a polysilox-ane-polystyrene block copolymer (or a multiblock copolymer) with terminal polysiloxane segments that can also bear aldehyde ends. These, in turn, can initiate the polymerization of other polystyrene segments and ultimately larger multiple segment block copolymers can be formed. 

From a fundamental physico-chemical point of view, a need exists to compare polyphosphazenes directly with closely related structural analogues in other areas of polymer chemistry. For example, valuable comparisons could be made between polyphosphazenes on the one hand and poly(organosiloxanes) or poly(aldehydes) on the other. Unfortunately, such direct comparisons are not yet possible. The structural analogue of poly(dimethylsiloxane), i.e. [NP(CH3)2]n> not yet been synthesized. Polysiloxanes with alkoxy, aryloxy, or amino residues as the sole side groups are not available. No polyphosphazenes have yet been prepared with two hydrogen atoms on each phosphorus to provide a comparison with poly(oxymethylene). Thus, many synthetic challenges still remain. 

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