Inorganic condensation polymers

Hyperbranched polyurethanes have also been synthesized by step-growth polymerization reactions such as the reaction between 3,5-diaminobenzoic acid and 

2-hydroxypropyl[3, 5-bis (benzoxycarbonyl)imino ]benzyl ether to prepare an AB2-type blocked isocyanate monomer functionalized with an ester group [35]. Several years earlier, Barmar et al. had reported the preparation of a polyurethane-based thickener starting from an ethoxylated urethane prepolymer that was reacted with polyethylene glycol and dicyclohexylmethane diisocyanate [36], 

Polysilanes, which are only slightly different from polysiloxanes, are a class of interesting inorganic polymers that, depending on the molecular weight and lateral substitutions on the silane atom, could be useful as 

In order to produce polysilanes with controlled optical properties, the substituents have to be picked up properly thus, poly(alkyl(methoxyphenyl)silane) homo and copolymers are reported by Nakashima and Fujiki [40], who found that poly(alkyl(alkoxyphenyl)silane) with methyl, ethyl and n-hexyl moieties showed a typical absorption peak around 340-360 nm atUibuted to the delocalized cr-conjugation. 

Other combinations, such as doped poly(disilanylene-oligothienylenejs, have been prepared [41] (Fig. 3.13), that are photoconducting when irradiated with visible light at 480 nm. 

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Among platy substances one may include such naturally occurring inorganic condensation polymers as... 

In the preparation of simultaneous networks, it is important to control both polymerizations rates. Systems with inorganic condensation rates much faster than the organic polymerization rates turn into brittle hybrids that shrink. The polymer content is low due to evaporation of unreacted monomer. Systems with fast organic polymerization rates usually show uncontrolled polymer precipitation leading to heterogeneous composites. In practice, the kinetics of polymerization are difficult to control, so the success of the simultaneous approach rests on the careful selection of the monomers and their composition. 

In many respects, the polyphosphazenes are the prototype inorganic backbone polymers, that exemplify the principles of ring-opening and condensation polymerization, macromolecular substitution reactions and their potential for molecular design, and an enormous range of derivatives with the same backbone but different organic side groups. 

Condensation polymers are classified as polyesters, polyamides, polyurethanes, and ether polymers, based on the internal functional group being ester (-COO-), amide (-CONH-), urethane (-OCONH-), or ether (-0-). Another group of condensation polymers derived by condensation reactions with formaldehyde is described under formaldehyde resins. Polymers with special properties have been classified into three groups heat-resistant polymers, silicones and other inorganic polymer, and functional polymers. Discussions in all cases are centered on important properties and main applications of polymers. 

Polymer 2 (Fig. 4.1) is an example of a condensation polymer where a difionctional cyclophosphazene can react with an organic or an inorganic difiinctional reagent to afford a linear polymer. These polymers contain the cyclophosphazene ring as a repeat motif in the polymer backbone. These polymers have also been termed cyclolinear polymers. In this type of polymers also, the scope for variation is considerable, although in practice this has not been realized. Polymers of the type 3 (Fig. 4.1) are examples of in-termolecularly crosslinked cyclophosphazenes. These are reminiscent of thermoset polymers such as phenol-formaldehyde or melamine-formaldehyde resins. The presence of the cyclophosphazene units in the crosslinked matrix is expected to impart special properties. However, this family of polymers also has not yet fulfilled the promise that they seem to hold. 

Figure 3.58 Separation of inorganic and organic anions as a function of the reaction cycle number with a BDDGE-methyl amine-based hyperbranched condensation polymer. Column dimensions 250 mm x 4 mm i.d. column temperature 30 °C eluent 5 mmol/L KOH (EG) flow rate 1 mlVmin detection ...

Hydroxide-Selective Hyperbranched Condensation Polymers As an alternative to carbonate-selective hyperbranched condensation polymers described above, which are typically used for conventional anion-exchange chromatography of common inorganic anions, a larger number of hydroxide-selective stationary phases have been developed following the same synthetic method. The technical characteristics of these columns are summarized in Table 3.9. 

The process uses a combination of hydrolysis and condensation reactions which lead to the formation of purely inorganic or hybrid inorganic-organic polymer... 

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