Polytetrahydrofuran Polytetramethylene Glycols

Polytetrahydrofuran (PTHF) is a polyether obtained by cationic ring opening polymerisation of tetrahydrofuran (THF), a five membered cyclic ether  

Triflic ester Triflic anhydride Fluorosulfonic acid 

The ring opening polymerisation of THF has as active centres tertiary oxonium cations and is based on the nucleophilic attack of the oxygen atom of the THF monomer at the a-carbon atom of the oxonium cation. The a-carbon atom is activated by the presence of the neighbouring positive charge which decreases the electron density at this carbon atom. Thus, the nucleophilic attack of the oxygen atom of the monomer takes place at the activated a-carbon atom (reaction 7.1) [3, 7]  

In the cationic polymerisation of THF, very small quantities of cyclic compounds (cyclic oligomers of THF) are formed (less than 3%), this is much lower than in alkyleneoxide cationic polymerisation [10, 11]. The cyclic oligomers are formed by the intramolecular nucleophilic attack of the etheric oxygen of the polymeric chains on the carbon atom from a position of the trialkyloxaonium chain end (reactions 7.2). 

The ceiling temperature (Tc) of THF cationic polymerisation is around 83 °C [3, 7, 35, 36, 38]. Above the ceiling temperature the transformation of THF in PTHF is practically impossible from the thermodynamic point of view. Tc is the temperature at which the variation of the monomer to polymer transformation free energy is zero (it is well known that a transformation takes place only at a negative variation of free energy, AG 0). The value of Tc in polymerisation is given by relationship 7.4. 

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Glycols, polyethylene, mono (p-(1,1,3,3-tetramethylbutyl) phenyl) ether. See Octoxynol Glycols, polytetramethylene. See Polytetrahydrofuran Polytetramethylene ether glycol... 

PTHForPTMO) polytetrahydrofurane or polytetramethylene oxide or poly (tetramethylene ether) glycol... 

The polyol employed may be a polyether or a polyester. Du Pont use polytetramethylene ether glycol (polytetrahydrofuran, poly(l,4-oxybutylene glycol)) for Lycra whilst US Rubber originally used a polyester of molecular weight c. 2000 made by condensing adipic acid with a mixture of ethylene and propylene glycols for Vyrene. A polyether-based material, Vyrene 2, was introduced in 1%7. All of these polyols have terminal hydroxyl groups. 

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