Preparation of Narrow-Molecular-Weight-Distribution Poly(tetrahydrofuran)

Abstract

ABSTRACT:The preparation method for the monodisperse crystallizable polymer, poly(tetrahydrofuran), was studied over a wide range of molecular weights. Bulk polymerization of tetrahydrofuran (THF) was carried out by introducing THF monomer into a completely reacted trifluoroboron-THF---ethylene oxide catalyst-promoter system, with vigorous stirring. This initiation technique had no induction period. Both molecular weights and conversion increased linearly with reaction time. The molecular weight distribution evaluated by the sedimentation method as well as light scattering and osmometry was very sharp and Mwl JJiln was less than 1.01 even at the Mw=10 6 • When the polymerization is stopped at a low conversion (8 %), which is far from the equilibrium, the in-chain transfer reaction is negligible.KEY WORDS Poly(tetrahydrofuran) I Narrow Molecular WeightDistribution I Trifluoroboron-THF-Ethylene Oxide I CatalystPromoter I Impurity I Chain Transfer I Much progress has been made in the study of the physical properties of amorphous polymers since the preparation of monodisperse polystyrene by Szwarc. 1 It seems unnecessary to stress the importance of monodisperse crystallizable polymers in the study of polymer physics. A few monodisperse crystallizable polymers [poly(tetrahydrofuran), poly(ethylene oxide) have] been prepared.The purpose of this work is to study the preparation method for the monodisperse crystallizable polymer, poly(tetrahydrofuran) (PTHF), over a wide range of molecular weights. It was pointed oue·a that tetrahydrofuran (THF) can be polymerized on a living mechanism, by certain ring opening cationic initiators, and several papers 4 -10 have been published on the preparation of PTHF of narrow molecular weight distributions. However, these molecular weight distributions are not narrow enough and the molecular weight ranges covered are not wide enough. It is essential in the study of physical properties to have samples not only with sharp molecular weight distributions but also a wide molecular weight range.There are various cationic initiators presented in previous works: trifluoroboron (BF3)---ethylene Polymer

Stoichiometric and Catalytic Activation of Si−H Bonds by a Triruthenium Carbonyl Cluster, (μ3,η2:η3:η5-acenaphthylene)Ru3(CO)7: Isolation of the Oxidative Adducts, Catalytic Hydrosilylation of Aldehydes, Ketones, and Acetals, and Catalytic Polymerization of Cyclic Ethers

“…Polymerization of THF generally is initiated by strong acids . Trials to produce poly-THF of narrow molecular weight distribution attained success when the living polymerization was quenched at the initial stage of the reaction, where conversion of THF is low . There are only a few examples of high-molecular-weight poly-THF being produced in good conversion with relatively narrow molecular weight distribution .…”

Photoinduced living cationic polymerization of tetrahydrofuran. I. Living nature of the system and its application to the diblock copolymer synthesis

“…Thus, the cationic polymerization of THF is one of the bestdefined examples. The cationic living nature of poly-(THF) has been applied to the synthesis of terminally functional poly(THF), 8,9 block copolymers by sequential polymerization, 10,11 block copolymers by terminal functionalization followed by polymerization, 12 block copolymers by an ion-coupling reaction, 13 and graft copolymers. 14 In these systems, the living nature of cationic poly(THF) was attributed to the stabilization of the cationic propagating species of the cyclic oxonium ion by ion-pair formation with a less nucleophilic complex metal halide counteranions 15 such as hexafluorophosphate, hexafluoroarsenate, and tetrafluoroborate.…”

Photoinduced living cationic polymerization of tetrahydrofuran(IV): Syringe method

“…The living nature of the cationic polymerization of THF is due to the stabilization of the propagating cationic species by ion pair formation with the less‐nucleophilic complex metal halide anion (PF) supplied by the initiator 1–3. However, the cationic propagating species is partially consumed by the attack of basic impurities, which in this case is water.…”

“…Living polymers have been the subject of extensive studies because living polymer systems enable us to synthesize monodispersed1 and terminally functional polymers,2, 3 block copolymers by sequential polymerization,4, 5 block copolymers by terminal functionalization followed by polymerization,6 block copolymers by an ion‐coupling reaction, and graft copolymers 7…”