Polyformals, aromatic

Watanabe [89] has used ultrasound in the synthesis of aromatic polyformals. Using a condensation reaction between a dihaloalkane and diphenol (Fig. 5.46) he was able to show that in the presence of ultrasound higher yields and larger molar masses were obtained. 

Spin Relaxation and Local Motion in a Dissolved Aromatic Polyformal... 

Spin relaxation in dilute solution has been employed to characterize local chain motion in several polymers with aromatic backbone units. The two general types examined so far are polyphenylene oxides (1-2) and aromatic polycarbonates (3-5) and these two types are the most common high impact resistant engineering plastics. The polymer considered in this report is an aromatic polyformal (see Figure 1) where the aromatic unit is identical to that of one of the polycarbonates. This polymer has a similar dynamic mechanical spectrum to the impact resistant polycarbonates (6 ) and is therefore an interesting system for comparison of chain dynamics. 

Polyformals containing secondary allylic and benzylic groups undergo complete acidolytic decomposition to volatile products such as an aromatic com-... 

In a works number [92, 93] the systematic change of molecular weight MM for copolymers aromatic copolyethersuUbnes (APESF) with their composition was marked, namely, aromatic polyformal blocks contents enhancement results to MM reduction. This observation was explained within the frameworks of special chemical approaches, for example, by cyclic ohgomers formation [92]. 

Let us make two remaiks in conclusion. As the estimations have shown, the constant coefficient in square brackets of the Eq. (58) does not always give the exact MM estimation and, probably, is adjustable coefficient Secondly, as Kucha-nov pointed out in annotations to paper [96], in polymerization real processes intramolecular reactions resulted to cyclic fragments formation, that makes aggregation models, similar to the considered above, application scarcely probable. However, Kolb [97] demonstrated, that loops (cycles) availability did not infln-ences on the value D. Therefore the present model is applicable to polymers, forming cyclic fragments, which aromatic polyformals are [92]. 

The stated above results on APESF example have shown, that copolymers molecular weight systematic reduction at aromatic polyformal blocks contents increase has key reasons. Molecular coil growth and, hence, molecular weight increase ceases, when coil density reduces up to the environment density. This transition is defined by macromolecular coil fractal dimension D. and polymer elementary link average weight m,. 

An aromatic polyformal was also prepared from bisphenol-A and methylene chloride by phase-transfer-catalyzed etherification in the presence of 2-(p-hydroxyphenyl)-2-oxazoline as an encapping agent. A polyformal with two oxazoline chain ends was obtained. When a mixture of DMSO and CH2CI2 was used as a solvent rather than only CH2CI2, a pol3nner with both oxazoline and... 

Earlier, we have synthesized polyformal oximates (PFO) on the basis of di-aeetophenyloxid dioxime and methylene eloride. The aromatic polyether has possessed a new eonjunetion of chemical fragments in a polymeric chain due to a structure of the initial monomers [2],... 

Aromatic polyformals cannot be synthesized by an extension of this chemistry. Reaction of aromatic phenols or bisphenols with formaldehyde does not give the formal derivatives derived from 0-alkylation but instead produces the well known phenol-formalde-hyde resins which result from C-alkylation of the phenol (equation 3). As a result, an alternate to formaldehyde must be found to supply the methylene group of the formal linkage. Barclay first reported such an approach in 1962 when he reacted the... 

These preliminary results suggest that aromatic polyformals such as 6 may have better oxidative and chemical stability than would have been predicted based on the reactivity of aliphatic formals. However, the effect of long term aging (either to oxidative or chemical environments) on the properties of have not been determined. 

Preliminary information on new aromatic polyformals based on other bisphenols is contained in Table 7. Most of these materials have been made only once and no extensive characterization of the polymers has been made. None of these polyformals were examined for cyclic oligomers. Where possible, the T for the corresponding polycarbonate is also given. All polymerizations were run in NMP/ CH9CI9 mixtures except when the bisphenol contained an electron 0... 

A variety of new aromatic polyformals and copolyformals with a wide range of Tg s have been prepared from other less commercially attractive bisphenols. No additional information regarding other properties or their propensity to form cyclics is known for these systems. To date, we have been unsuccessful in obtaining homogeneous blends of BPA polyformal with other polymer systems. 

High-Performance Polymers Aromatic Heterocyclic Monomers Thermally Stable Polymers High-Performance Composites Reactive Oligomers Aromatic Polyformals Star and Comb Shape Copolymers Polymers in Phase Transfer Catalysis Organometallic Polymers Poljmiers in Medical Applications Nitrogen-Containing Polymers Vinyl Organometallic Monomers Functionalized Polymers Anionic Copolymerizations Macromers... 

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