COPOLYETHER

A number of patents cl aim THF copolymers by direct copolymerization of THF and other cycHc ethers (168,256—259). Although samples of THF copolyethers are available occasionally, none had any industrial importance as of 1996. 

The polymers obtained by this copolymerization [103] show weight average molecular weights upto 2 x 10. Such functionalized copolyethers are of interest for preparation of membranes with variable hydrophilicity and permeability [104]. 

These materials are segmented copolyether esters formed by the melt transesterification of dimethyl terephthalate, poly(tetramethylene ether) glycol and 1,4-butane diol. As with the thermoplastic polyurethanes, one can describe a hard segment and a soft segment, the hard segments forming crystalline areas which act as pseudocrosslinks . 

The following gives representative properties of the copolyether esters ... 

These materials exhibit the same type of morphology as the copolyether esters, the polyamide providing the hard segment, and the polyester the soft elastomeric phase. The service temperature is lower than that of the copolyether esters, but apart from this difference they exhibit similar properties. 

Scheme 7. Synthetic avenues used for the synthesis of 4,4 -dihydroxy-biphenyl polyethers and copolyethers.

COOLING RATE, 271 273 315 COOLING TIME, 62 73 COPOLYETHER, 107 COPOLYMER, 180 197 279 COPOLYMER COMPOSITION, 8 103 136 239... 

Scheme 6. Synthesis of Block Copolyethers with Regularly Placed Functional Groups.

Kambour RP, Romagosa EE, Gruner CL (1972) Swelling, crazing, and cracking of an aromatic copolyether-sulfone in organic media. Macromolecules 5(4) 335-340... 

Substrate materials included poly (dimethyl siloxane) (SR) (Silastic Rubber, medical grade, Dow Corning), fluorinated ethylene/propylene copolymer (FEP) (Teflon FEP, Dupont), and a segmented copolyether-urethane-urea (PEUU) based on poly (propylene glycol), methylene bis-4-phenylisocyanate, and ethylenediamine. This PEUU was provided by D. J. Lyman. 

Figure 4. Crystal-isotropic (k-i), crystal-nematic (k-n), and nematic-isotropic (n-i) transition temperatures as a function of mole fraction of -(Cl ) q- spacer pertaining to the series of MBPE-8,10 copolyethers, containing methylbiphenyl ethane mesogen and randomly distributed -(CH,)0- and -(CH,).n- spacers (adapted from ref. 15).

Sasaki, K. Yazaki, Y Block Copolyether Ester Compositions. Japanese Patent No. 61,091,245, May 9 Showa, 1986. 

To a degree, the mechanical properties of copolyether esters depend upon the conditions under which the sample is allowed to crystallize. Polymers having 4GT hard segments crystallize very rapidly compared with some other terephthalate copolymers. This is apparent from the rate of hardness development of injection-molded samples. Figure 17 compares the hardness of injection moldings at a 57% 4GT/PTMEG-T copolymer with that of a 2GT copolymer at various times after ejection... 

Figure 17. Hardening rate of injection-molded samples of copolyether esters. Melt temperature is 240°C mold temperature is 30°C 58% 4GT/PTMEG-T (A), 56% 2GT/PTMEG-T (B)...

Figure 6. Comparison of PTMEG and EO/THF copolyether glycols stressing significant property differences.

Ozden S, Charaev A M., Shaov A.H. High impact thermally stable blok- copolyethers. J. Mater. Sci. - 2001.-36.-P. 4479-4484. 

Description of termotropic liguid-ciystalline copolyether polyethyleneterephtalat and terephtaloyl-di(n-oxybenzoat) is given in this work [2], Microstructure of given block-copolymer is characterized by means of IR-spectroscopy with fourie-transformation. Pictures of polarization microscopy show, that copolyether is nematic liguid-crystalline polymer. 

Unfortunately, DMC catalysts are not efficient for EO polymerisation, and it is practically impossible to obtain PO-EO block copolymers with this catalyst. Acidic catalysts are not used on an industrial scale for alkylene oxide polymerisation due to the formation of substantial amounts of cyclic ethers as side products. Acidic catalysts are used industrially only for the synthesis of polytetrahydrofuran polyols or, to a lesser extent, for tetrahydrofuran - alkylene oxide copolyether polyol fabrication (see Sections 7.1, 7.2 and 7.3) Other catalysts have a minor importance for large scale polyether polyol production. 

The random copolyether triols PO-EO, usually called heteropolyether polyols, with a MW of 3000-3600 daltons, are the most important polyether polyols for flexible PU slabstock foams, generally used in furniture industry. The worldwide consumption of flexible PU foams is presented in Figure 4.16. 

It can be seen that moulded flexible PU foams using EO capped polyether polyols (block copolymers PO-EO with terminal poly[EO] block) represent only 22% of total worldwide consumption and that the majority of foams are flexible slabstock PU foams which use random copolyethers of PO-EO. It can therefore be concluded that the most important polyols for flexible PU foams production are in fact the random copolyethers PO-EO. 

Practically, the synthesis of random copolyethers of PO-EO is very similar to the synthesis of polyether PO homopolymers, with the difference that the starter (mainly glycerol) is reacted with an homogeneous mixture of PO-EO, containing around 10-15% EO, instead of PO alone. 

It is not possible for EO to isomerise to the allyl structure. As an immediate consequence, the unsaturation of the random copolyethers, PO-EO, is lower than the unsaturation of analogue PO homopolymers, at the same MW [75]. 

The increased propagation rate, due to the presence of EO, a monomer more reactive than PO, is another explanation for the resulting lower unsaturation of random PO-EO copolyethers. 

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