Synthesis and properties of poly(cis-1,4-dihydroxy-2,3-epoxybutane)

The cyclic acetone ketal of 1,4-dihydroxy-2,3-epoxybutane (DMTO) polymerizes with i-Bu₃Al-0.7 H₂O catalyst by a cationic mechanism at ?78°C to a moderate molecular weight (η_inh up to 0.7), atactic (based on ¹³C-NMR) polymer (PDMTO). At higher temperature and in bulk, up to 14% crosslinked polymer is obtained as a result of epoxide and ketal ring opening. Triethylaluminum is an effective catalyst at 0–50°C in bulk. Coordination catalysts were less effective but the results indicate that an effective one can be designed. PDMTO is readily hydrolyzed with aqueous HCl treatment to atactic, water-soluble poly(1,4-dihydroxy-2,3-epoxybutane) (PDHEB) with a T_g of 80°C. PDHEB is melt stable to 200°C and can be molded to give brittle, clear films that readily pick up 5–10% H₂O from the atmosphere to give properties like those of plasticized poly(vinyl chloride). PDHEB is degraded by electron beam radiation but can be crosslinked with glyoxal plus toluene sulfonic acid/The bis(trimethylsilyl) ether of cis-1,4-dihydroxy-2,3-epoxybutane was polymerized cationically with the i-Bu₃Al-0.7 H₂O catalyst at ?78°C to a fairly tactic, presumably racemic di-isotactic, amorphous polymer, with η_inh of 0.16. A mechanism is proposed for this stereoregular polymerization based on a complexation of the Si side group of the last chain unit with the propagating oxonium on.     

Polymerization of glycidol and its derivatives: A new rearrangement polymerization

Anionic (KOH) polymerization of glycidol, or its trimethylsilyl ether (TMSGE) followed by hydrolysis, gives a low molecular weight, largely amorphous polymer that is not the reported 1,3-polyglycidol but, based on ¹³C-NMR, largely a 1,4-poly(3-hydroxyoxetane) with much branching. This result is achieved by a simple rearrangement of the usual, propagating secondary oxyanion to a primary one. Substantial amounts of four dimers (5–10%), four trimers, and some tetramers were also found. One dimer was isolated and shown to be glycidyl glycerin, the usual thermal dimer from glycidol. Possible structures of the other dimers are proposed. The polymerization appears to begin with the rapid formation of the glycidoxy anion , formed by base abstraction of a proton from glycidol and by nucleophilic displacement of the SiMe₃ group from TMSGE. Other bases such as KOtert-Bu give similar 1,4 polymer for glycidol but, with TMSGE, there is considerable 1,3 polymerization. Detailed mechanisms are proposed. The polymer perpared from R-TMSGE with KOH was highly crystalline, high melting (166°C), H₂O soluble, isotactic poly(3-hydroxyoxetane). The cationic polymerization of tert-butyl glycidyl ether (TBGE) and TMSGE gave low molecular weight 1,3 polyethers. The TBGE polymer was all head-to-tail whereas the polyglycidol from TMSGE contained extensive head-to-head chain units with considerable branching. Mechanisms for these interesting differences are proposed.     

Stereoregularity of poly(2-vinylpyridine) and poly-(4-vinylpyridine)

In order to determine the stereoregularity of poly(4-vinylpyridine), 4-vinylpyridine-β,β-d₂ was synthesized from 4-acetylpyridine. The ¹H-NMR spectra of the deuterated and nondeuterated polymers were measured and analyzed. From the ¹H-NMR spectra of poly(4-vinylpyridine-β,β-d₂), triad tacticity can be obtained, while the ¹H-NMR spectra of nondeuterated poly(4-vinylpyridine) give the fraction of isotactic triad. The ¹³C-NMR spectra of poly(4-vinylpyridine) were also observed, and the spectra of C₄ carbon of polymers were assigned by the pentad tacticities. The fraction of isotactic triad of poly(2-vinylpyridine) and poly(4-vinylpyridine) obtained under various polymerization conditions were determined. The radical polymerization and anionic polymerizations with phenylmagnesium bromide and n-butyllithium as catalysts of 4-vinylpyridine gave atactic polymers.     

Synthesis of biocompatible and biodegradable block copolymers of polyvinyl alcohol‐block‐poly(ε‐caprolactone) using metal‐free living cationic polymerization

Applications of metal‐free living cationic polymerization of vinyl ethers using HCl · Et₂O are reported. Product of poly(vinyl ether)s possessing functional end groups such as hydroxyethyl groups with predicted molecular weights was used as a macroinitiator in activated monomer cationic polymerization of ε‐caprolactone (CL) with HCl · Et₂O as a ring‐opening polymerization. This combination method is a metal‐free polymerization using HCl · Et₂O. The formation of poly(isobutyl vinyl ether)‐b‐poly(ε‐caprolactone) (PIBVE‐b‐PCL) and poly(tert‐butyl vinyl ether)‐b‐poly(ε‐caprolactone) (PTBVE‐b‐PCL) from two vinyl ethers and CL was successful. Therefore, we synthesized novel amphiphilic, biocompatible, and biodegradable block copolymers comprised polyvinyl alcohol and PCL, namely PVA‐b‐PCL by transformation of acid hydrolysis of tert‐butoxy moiety of PTBVE in PTBVE‐b‐PCL. The synthesized copolymers showed well‐defined structure and narrow molecular weight distribution. The structure of resulting block copolymers was confirmed by ¹H NMR, size exclusion chromatography, and differential scanning calorimetry. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5169–5179, 2009     

Cationic polymerization of vinyl monomers initiated by 10-methylphenothiazine cation radicals

A small quantity of 10-methylphenothiazine cation radical (MPT^.+), electrochemically prepared and stocked in acetonitrile solution, initiated cationic polymerizations of n-butyl, t-butyl, and 2-methoxyethyl vinyl ethers and p-methoxystyrene, while no initiation occurred for phenyl vinyl ether, styrene, methyl methacrylate, and phenyl glycidyl ether. ¹H-NMR studies of oligomers and low molecular weight compounds isolated from the reaction mixture for the polymerization of t-butyl vinyl ether in the presence of a small amount of D₂O indicated that electron transfer from the monomer to MPT^.+ was involved in the initiation step. ¹H- and ¹³C-NMR and MO calculation implied that monomers with higher electron densities on the vinyl groups and with lower ionization potentials were more susceptible to the initiation of MPT^.+. © 1994 John Wiley & Sons, Inc.     

Synthesis of heteroarm star polymers comprising poly(4-methylphenyl vinyl sulfoxide) segment by living anionic polymerization

<正>A series of 3-arm ABC and AA'B and 4-arm ABCD,AA'BC and AA′A″B heteroarm star polymers comprising one poly(4-methylphenyl vinyl sulfoxide) segment and other segments such as polystyrene,poly(α-methylstyrene), poly(4-methoxystyrene) and poly(4-trimethylsilylstyrene) were synthesized by living anionic polymerization based on diphenylethylene(DPE) chemistry.The DPE-functionalized polymers were synthesized by iterative methodology,and the objective star polymers were prepared by two distinct methodologies based on anionic polymerization using DPE-functionalized polymers.The first methodology involves an addition reaction of living anionic polymer with excess DPE-functionalized polymer and a subsequent living anionic polymerization of 4-methylphenyl vinyl sulfoxide(MePVSO) initiated from the in situ formed polymer anion with two or three polymer segments.The second methodology comprises an addition reaction of DPE-functionalized polymer with excess sec-BuLi and a following anionic polymerization of MePVSO initiated from the in situ formed polymer anion and 3-methyl-1,1-diphenylpentyl anion as well.Both approaches could afford the target heteroarm star polymers with predetermined molecular weight,narrow molecular weight distribution (M_w/M_n1.03) and desired composition,evidenced by SEC,~1H-NMR and SLS analyses.These polymers can be used as model polymers to investigate structure-property relationships in heteroarm star polymers.     

Structural irregularities in poly(vinyl alcohol)

Poly(vinyl alcohols) derived from the product of polymerization of vinyl acetate in methanol have been characterized by various physical and chemical methods before and after NaIO₄ cleavage. The 220-MHz ¹H-NMR spectra confirm the reliability of NaIO₄ titrimetry for estimating 1,2-glycol content and help explain the tendency for viscometry to grossly underestimate the 1,2-glycol content for low molecular weight polymers. The spectra and related chemical evidence indicate that the major endgroups are HOCH₂CH₂? and CH₃CH(OH)CH(OH)CH₂? . ß-Hydroxyethyl groups also occur as short chain branches, mainly attached to α carbon atoms in the normal head-to-tail polymer chain sequence. The concentrations of the branch and endgroups depend on polymerization conditions and help explain polymerization “solvent” effects on physical properties.     

H(OEt2)2[P(1,2‐O2C6Cl4)3]: Synthesis,Characterization, and Application as a Single‐Component Initiator for the Carbocationic Polymerization of Olefins

The development of novel Brønsted acids featuring the hexacoordinate phosphorus(V) anion [TRISPHAT]^? {[ 1 ]^?=[P(1,2‐O₂C₆Cl₄)₃]^?} are reported. The title compound, H(OEt₂)₂[ 1 ], was synthesized from 1,2‐(HO)₂C₆Cl₄ (3 equiv) and PCl₅ in the presence of diethyl ether. This compound was fully characterized by ¹H, ³¹P and ¹³C NMR spectroscopy, X‐ray crystallography and elemental microanalysis. Dissolution of H(OEt₂)₂[ 1 ] in acetonitrile results in the slow precipitation of crystalline H(OEt₂)(NCMe)[ 1 ], which was characterized by X‐ray diffraction; however, in CD₂Cl₂ solution the [TRISPHAT]^? anion protonated and ring‐opened. The weighable, solid H(OEt₂)₂ [ 1 ] was found to be a competent initiator for the polymerization of n‐butyl vinyl ether, α‐methylstyrene, styrene and isoprene at a variety of temperatures and monomer‐to‐initiator ratios. At low temperatures, polymers with M_n>10⁵ were obtained for n‐butyl vinyl ether and α‐methylstyrene whereas slightly lower molecular weights were obtained with styrene and isoprene (10⁴<M_n<10⁵). The poly(α‐methylstyrene) synthesized at ?78 °C is syndiotactic‐rich (ca. 87 % rr) whereas the polystyrene obtained at ?50 °C is atactic. The polyisoprene obtained possessed all possible modes of enchainment as well as branched and/or cyclic structures that are often observed in polyisoprene.     

High molecular weight atactic polypropene synthesized with (η5‐pentamethylcyclopentadienyl)tribenzyl titanium activated with MAO

The half‐titanocene (η⁵‐pentamethylcyclopentadienyl)tribenzyl titanium (Cp*TiBz₃) with methylaluminoxane (MAO) as the cocatalyst was employed to catalyze propene polymerization at ambient pressure. A novel atactic polypropene elastomer with a high molecular weight (M̄_w = 2 − 8 × 10⁵) was produced. The effects of the polymerization conditions on the catalytic activity and polymer molecular weight are discussed. ¹³C NMR analysis confirmed that the catalyst system Cp*TiBz₃/MAO produced atactic polypropenes, and the polymerization mechanism was in agreement with the Bernoullian process. The triad sequence distribution of the polymer was measured and found to be as follows: mm = 6.15%, mr = 40.87%, and rr = 52.98% (Bernoullian factor B = 1.03); this indicated that the insertion of propene with the catalyst system followed a chain‐end control model. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 411–415, 2000     

Cationic RAFT Polymerization Using ppm Concentrations of Organic Acid

A metal‐free, cationic, reversible addition–fragmentation chain‐transfer (RAFT) polymerization was proposed and realized. A series of thiocarbonylthio compounds were used in the presence of a small amount of triflic acid for isobutyl vinyl ether to give polymers with controlled molecular weight of up to 1×10⁵ and narrow molecular‐weight distributions (M_w/M_n<1.1). This “living” or controlled cationic polymerization is applicable to various electron‐rich monomers including vinyl ethers, p‐methoxystyrene, and even p‐hydroxystyrene that possesses an unprotected phenol group. A transformation from cationic to radical RAFT polymerization enables the synthesis of block copolymers between cationically and radically polymerizable monomers, such as vinyl ether and vinyl acetate or methyl acrylate.     

End-Functionalized polymers by living cationic polymerization. IV. Poly(vinyl ethers) with acidic or basic terminal groups by functional initiator method

Carboxylic acid or primary amine-terminated poly(isobutyl vinyl ethers) were synthesized by living cationic polymerizations with functionalized initiators (CH₃CHIO? CH₂CH₂ ? X; X: that are the adducts of the corresponding vinyl ethers (CH₂ ? CH ? OCH₂CH₂? X) with hydrogen iodide. In the presence of iodine, these initiators induced living cationic polymerization of isobutyl vinyl ether to give polymers with the α-end group of X originating from the initiators. The polymer molecular weights were regulated by the monomer to initiator feed ratio and the molecular weight distributions were very narrow (M _w/M _n ≤ 1.15). Subsequent deprotection of the terminal group X led to polymers with a terminal carboxylic acid or primary amine. ¹H- and ¹³C-NMR analyses showed that the end functionalities of these polymers were all close to unity.     

Cationic polymerization of isobutyl vinyl ether initiated with transition‐metal ate complexes

The cationic polymerization of isobutyl vinyl ether was examined with transition‐metal ate complexes with trityl cation as initiators. The initiators were generated by the reaction of triphenylmethyl chloride [trityl chloride (TrCl)] with ate complexes of Nb, Mo, and W with lithium cation, which were obtained in situ by the reaction of the transition‐metal halides with anionic reagents (organolithium or lithium amide). When the polymerization was initiated with a mixture of TrCl and Li⁺[NbH₅(NnBuPh)]^?, the resulting poly(isobutyl vinyl ether)s had narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight = 1.13–1.20). Although the polymerization was supposed to be initiated by the electrophilic attack of the trityl cation, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry analysis of the resulting poly(isobutyl vinyl ether)s revealed the presence of H at the α‐chain end. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2636–2641, 2006     

Polymerization of vinyl chloride catalyzed by a titanium complex with an anionic oxygen tripod ligand

Poly(vinyl chloride) (PVC) was prepared using a titanium complex with an anionic oxygen tripod ligand [CpCo{P(O)(OEt)₂}₃]⁻ () as catalyst and methyl aluminoxane (MAO) as cocatalyst. The polymerization behavior was compared with that of pentamethyl cyclopentadienyl titanium trichloride (Me₅CpTiCl₃). It is observed that L_OEtTiCl₃ can polymerize vinyl chloride with activity comparable to that of Me₅CpTiCl₃. The PVC samples prepared with L_OEtTiCl₃/MAO exhibit bimodal molecular weight distribution and the fraction of high molecular weight peak decreases with polymerization temperature. The microstructure and thermal decomposition of the PVC obtained were studied. Five types of structural defect were detected by ¹H-NMR. Only saturated structural defects are found at low polymerization temperature, but at high polymerization temperature unsaturated structural defects, possibly resulting from dehydrochlorination of the saturated structural defects, appear as well. No head-to-head structural defect is observed. ¹³C-NMR shows that the PVC prepared by L_OEtTiCl₃ has an atactic stereostructure. Compared with the PVC from radical polymerization and anionic polymerization, the PVC samples prepared with L_OEtTiCl₃ show improved thermal stability.     

Living cationic polymerization of vinyl ethers with a functional group. VII. Polymerization of vinyl ethers with a silyloxyl group and synthesis of polyalcohols and related functional polymers

Living cationic polymerizations of two silicon-containing vinyl ethers, 2-(t-butyldimethyl-silyloxyl)ethyl vinyl ether (tBuSiVE) and 2-(trimethylsilyloxyl)ethyl vinyl ether (MeSiVE), have been achieved with use of the hydrogen iodide/iodine (HI/I₂) initiating system in toluene at ?15 or ?40°C, despite the existence of the acid-sensitive silyloxyl pendants. The living nature of the polymerizations was demonstrated by linear increases in the number-average molecular weights (M?_n) of the polymers in direct proportion to monomer conversion and by their further rise upon addition of a second monomer feed to a completely polymerized reaction mixture. The polymers obtained in these experiments all exhibited very narrow molecular weight distributions (MWD) with M?_w/M?_n around or below 1.1. Desilylation of the polymers under mild conditions (with H⁺ for MeSiVE and F^? for tBuSiVE) gave poly(2-hydroxyethyl vinyl ether), a water-soluble polyalcohol with a narrow MWD. The living processes also permitted clean syntheses of amphiphilic AB block copolymers and water-soluble methacrylate-type macromonomers, all of which bear narrowly distributed segments of the polyalcohol derived from the silicon-containing vinyl ethers.     

Polymers derived from fluoroketones. III. Monomer synthesis,polymerization, and wetting properties of poly(allyl ether) and poly(vinyl ether)

The synthesis and polymerization of a series of perhaloalkyl allyl and vinyl ethers derived from perhaloketones is described. Data on the critical surface tension of wetting (γ_c) for high molecular weight polymers of heptafluoroisopropyl vinyl ether and low molecular weight poly(heptafluoroisopropyl allyl ether) is also presented. Preparation of the allyl ethers is a one-step, high-yield displacement reaction between the potassium fluoride–perhaloacetone adduct and an allyl halide, such as allyl bromide. The vinyl ethersare prepared by a two-step process which involves displacement of halide from a 1,2-dihaloethane with a KF–perhaloacetone adduct and dehydrohalogenation of the 1-halo-2-perhaloalkoxyethane to a vinyl ether. Low molecular weight polymers were obtained with heptafluoroisopropyl allyl ether by using a high concentration of a free-radical initiator. The low molecular weight poly(heptafluoroisopropyl allyl ether) had a γ_c of 21 dyne/cm. No polymer was obtained with tributylborane–oxygen or with VCl₃–AIR₃, with gamma radiation, or by exposure to ultraviolet light. High molecular weight polymers were obtained from heptafluoroisopropyl vinyl either by using either lauryl peroxide or ultraviolet light but not by exposure to BF₃–etherate. The γ_c for poly(heptafluoroisopropyl vinyl ether) ranged from 14.2 to 14.6 dyne/cm., and the significance of this value is discussed in relation to the γ_c for poly(heptafluoroisopropyl acrylate).     

Living cationic polymerization of 2-vinyloxyethyl phthalimide: Synthesis of poly(vinyl ether) with pendant primary amino functions

Cationic polymerization of 2-vinyloxyethyl phthalimide ( 1 ) in CH₂Cl₂ at ?15°C with hydrogen iodide/iodine (HI/I₂) as initiator led to living polymers of a narrow molecular weight distribution (M?_w/M?_n = 1.1–1.25). The number-average molecular weight of the polymers was in direct proportion to monomer conversion and could be controlled in the range of 1000–6000 by regulating the 1 /HI feed ratio. However, when a fresh monomer was supplied to the completely polymerized reaction mixture, the molecular weight of the polymers was not directly proportional to monomer conversion. The polymerization of 1 by boron trifluoride etherate (BF₃OEt₂) in CH₂Cl₂ at ?78°C gave polymers with relatively high molecular weight (M?_w > 20,000) and broad molecular weight distribution (M?_w/M?_n ～ 2). The HI/I₂-initiated polymerization of 1 was an order of magnitude slower than that of ethyl vinyl ether, probably because of the electron-withdrawing phthalimide pendant. Hydrazinolysis of the imide functions in poly( 1 ) gave a water-soluble poly(vinyl ether) ( 3 ) with aliphatic primary amino pendants.     

MECHANISM-TRANSFORMATION SYNTHESIS AND CHARACTERIZATION OF POLY(STYRENE-b-2-ETHYL-2-OXAZOLINE) DIBLOCK COPOLYMER*

By mechanism-transformation (anionic→ cationic) poly(styrene- b-2-ethyl -2-oxazoline) diblockcopolymer, PS-b-PEOx, was synthesized in two steps. The first step is the polymerization of styrene blockcapped with ethylene oxide and its tosylation; the second step is the cationic ring-opening polymerization of2-ethyl-2-oxazoline. The products were thoroughly characterized by various methods, such as ~1H-NMR, IR,DMA, TEM and SAXS. The results show that the copolymer obtained possesses high molecular weight andnarrow molecular weight distribution.     

Synthesis of poly(β‐pinene)‐g‐poly(meth)acrylate by the combination of living cationic polymerization and atom transfer radical polymerization

New graft copolymers of β‐pinene with methyl methacrylate (MMA) or butyl acrylate (BA) were synthesized by the combination of living cationic polymerization and atom transfer radical polymerization (ATRP). β‐Pinene polymers with predetermined molecular weights and narrow molecular weight distributions (MWDs) were prepared by living cationic polymerization with the 1‐phenylethyl chloride/TiCl₄/Ti(OiPr)₄/nBu₄NCl initiating system, and the resultant polymers were brominated quantitatively by N‐bromosuccinamide in the presence of azobisisobutyronitrile, yielding poly(β‐pinene) macroinitiators with different bromine contents (Br/β‐pinene unit molar ratio = 1.0 and 0.5 for macroinitiators a and b , respectively). The macroinitiators, in conjunction with CuBr and 2,2′‐bipyridine, were used to initiate ATRP of BA or MMA. With macroinitiator a or b , the bulk polymerization of BA induced a linear first‐order kinetic plot and gave graft copolymers with controlled molecular weights and MWDs; this indicated the living nature of these polymerizations. The bulk polymerization of MMA initiated with macroinitiator a was completed instantaneously and induced insoluble gel products. However, the controlled polymerization of MMA was achieved with macroinitiator b in toluene and resulted in the desired graft copolymers with controlled molecular weights and MWDs. The structures of the obtained graft copolymers of β‐pinene with (methyl)methacrylate were confirmed by ¹H NMR spectra. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1237–1242, 2003     

Polymerization of 1‐hexene with bis[N‐(3‐tert‐butylsalicylidene)phenylaminato]titanium(IV) dichloride using iBu3Al/Ph3CB(C6F5)4 as a cocatalyst

1‐Hexene polymerization was investigated with bis[N‐(3‐tert‐butylsalicylidene)phenylaminato]titanium(IV) dichloride ( 1 ) using ⁱBu₃Al/Ph₃CB(C₆F₅)₄ as a cocatalyst. This catalyst system produced poly(1‐hexene) having a high molecular weight (M_w = 445 000–884 000, 0–60°C). ¹³C NMR spectroscopy revealed that the high molecular weight poly(1‐hexene) possesses an atactic structure with about 50 mol‐% of regioirregular units.     

Well phase separated segmented copolymers via acyclic diene metathesis (ADMET) polymerization

Segmented oligomers consisting of polyoctenylene hard segments and unsaturated polytetrahydrofuran soft segments were prepared using acyclic diene metathesis (ADMET) copolymerization techniques. These are the first such segmented materials prepared via metathesis chemistry. Two different molecular weight α,ω-poly(tetrahydrofuran)diene soft segment monomers of the structure [CH₂CH(CH₂)₄[O(CH₂)₄]-_nO(CH₂)₄CHCH₂] (1) were synthesized by the cationic living polymerization of tetrahydrofuran (THF). Trifluoromethanesulfonic anhydride, (CF₃SO₂)₂O (triflic anhydride) (2), was employed as the initiator, followed by in situ bis-functionalization with 5-hexen-1-ol, [CH₂=CH(CH₂)₄OH] (3), to yield soft segment dienes with vinyl end groups. The functionality of these soft segment monomers was approximately 1.9. These telechelic monomers possessed sufficient functionality to be homopolymerized or copolymerized with 1,9-decadiene (4) to generate well phase separated, segmented oligomers exhibiting hard segment/soft segment thermal behavior. The segmented copolymers were characterized by ¹H-NMR, ¹³C-NMR, and IR spectroscopy, elemental analysis, and TGA and DSC analysis. Average molecular weights were determined by gel permeation chromatography (GPC) and end-group analysis. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 3441–3449, 1997