The polymerization of tetrahydrofuran ( T H F) initiated by heteropolyacid H3 P W12 O40( P W12) in low concentration could be effectively promoted by propylene oxide( P O) . The polymerization conversion reached 50 % ～60 % after a reaction time around 5 h . Wateror butylene glycol was used to controlthe molecular weightofthe productin the rangeof 1000 ～3000 . The polymerization started upon addition of P Oand stopped with completeconsumption of P O,but it would start again when a new portion of P O was added . Theaverage hydroxyl end group functionality of polyether glycol is close to 2 . The ratio ofprimary and secondary hydroxyl end groups is close to one ,and the percentage of thehydroxyl group attached to P O moietiesatthe polymerchain endsis higherthan 50 % ofthetotal hydroxyl end groups. All the obtained results inferred that T H F polymerizationpromoted by P Oproceeded quite similar to that promoted by ethylene oxide,i.e., P O wasnecessary in theinitiation of T H Fpolymerization to startthe propagation ofchains,and withthe complete consumption of P Othe propagating chains transformed into dormant species,which can be re initiated by the addition ofa supplementary portion of P O.
Self assembly of an amphiphilic diblock copolymer polysyrene b polyvinylbenzoic acid in ethanol,which is a selective solvent for the polybenzoic acid segment was studied by means of transmission electron microscopy.The diblock copolymers can self assemble into nano scale aggregates with polystyrene segment as the core and polyvinylbenzoic acid segment as the corona.The morphology of the aggregates is mainly controlled by the ratio of the two segment of the diblock copolymer.As the content of the ethanol insoluble polystyrene segment increased,the morphology can be changed from spheres to rods.The diameter of the aggregates increases slightly with concentration and decreases with the addition of CoCl 2 salt.
The polymerzation of tetrahydrofuran (THF) initiated by heteropolyacid—H\-3PW\-\{12\}O\-\{40\} in low concentration could be promoted by oxetane (OX), but the polymerization stopped at lower conversion than that promoted by oxiranes. The chain structure analysis by NMR spectra showed that OX was more reactive toward polymerization than oxiranes and more than 80% of OX were consumed through copolymerization, but not initiation. By stepwise addition of OX the conversion of THF polymerization could be increased higher than 50%. The percentage of the hydroxyl group attached to OX moieties at the polymer chain\|ends was higher than 50% of the total hydroxyl end\|groups, inferring that polymerization proceeded quite similar to that promoted by ethylene oxide and each chain was started with the OX moiety.
The polymerization of tetrahydrofuran(THF) initiated by heteropolyacid—H 3PW 12 O 40 (PW 12 ) in low concentrations could be effectively promoted by epichlorohydrin(ECH).However, the promotion activity of ECH is lower than that of EO or PO, especially when water was introduced. The polymerization started upon addition of epichlorohydrin.When the polymerization has stopped, it could be re\|initiated with the addition of a new portion of ECH. The products were found to be copolyether glycols with hydroxyl groups at both ends.The percentage of the hydroxyl group attached to ECH moieties at the polymer chain\|ends was higher than 50% of the total hydroxyl end\|groups. Most of the ECH moieties in chains attached to hydroxyl end groups, and no primary hydroxyl groups derived from ECH could be detected.
Polyether triol with molecular weight distribution index being 1\^3～1\^5 was prepared in yield around 50% by tetrahydrofuran polymerization using heteropolyacid\|H\-3PW 12 O 40 and ethylene oxide as initiator system and 1,1,1\|trihydroxymethylenepropane(TMP) as molecular weight controller.The average hydroxyl functionality was estimated by end\|group analysis and VPO to be close or equal to 3. The 1H NMR spectra showed that about 1/3 hydroxyl of TMP did not react with the propagating chains in the THF polymerization.Each of the unreacted hydroxyl groups of TMP attached to the middle or to the end of a diol chain as a pendent primary hydroxyl group forming the obtained polyether triol. All the hydroxyls of polyether triol were verified to be active enough towards 4,4′ methylene bis(phenyl isocynate) in the preparation of polyurethanes.
