Regioselectively modified stereoregular polysaccharides, 12. Synthesis of (1→6)-α-linked polysaccharides consisting of D-glucose and 2,3,4-tri-O-octadecyl-D-glucose units

By ring-opening copolymerization of 1,6-anhydro-2,3,4-tri-O-octadecyl-β-D -glucopyranose ( 1 ) with 1,6-anhydro-2,3,4-tri-O-benzyl-β-D -glucopyranose ( 2 ) using phosphorus pentafluoride as initiator in dichloromethane at 0°C, stereoregular copolymers 3 , with M?_n = 6 · 10³ to 24 · 10³ were obtained. For debenzylation of copolymers 3 , either the reduction with sodium in liquid ammonia or radical bromination-hydrolysis was applied, depending on solubility and copolymer composition. Poly[2,3,4-tri-O-octadecyl-α-D -glucopyranosyl-(1→6)-stat-α-D -glucopyranosyl-(1→6)] ( 4 ,) exhibits characteristic solution properties arising from its amphiphilic structure. Polysaccharide 4 , with mole fractions of trioctadecylated unit (x) below 0,03, are water-soluble and interact with magnesium 1-anilino-8-naphthalenesulfonate (ANS) in water. The polysaccharide 4 (x = 0,29), which is soluble in chloroform, was found to solubilize an aqueous methyl orange solution in chloroform. Formation of micelles in water and reversed micelles in chloroform is suggested.     

Polymerization of bicyclic acetals, 14. Synthesis of an amphiphilic block copolymer via ring-opening polymerization of 6,8-dioxabicyclo[3.2.1]octane with a polysaccharide macroinitiator

A polysaccharide macroinitiator (M?_n = 5000 to 28000) ( 1 ), having a reactive chlorine atom at the reducing end, was prepared by ring-opening polymerization of 1,6-anhydro-2,3,4-tri-O-benzyl-β-D -glucose (TBLG) with antimony pentachloride as initiator in presence of acetyl chloride in dichloromethane at ?60°C. Macroinitiator 1 in combination with silver hexafluoroantimonate was found to induce the polymerization of 6,8-dioxabicyclo[3.2.1]octane (DBO) in tetrahydrofuran, 2-methyltetrahydrofuran, or tetrahydropyran at ?78 to 0°C. Fractionation of the reaction products gave a block copolymer ( 2 ) composed of poly(TBLG) and poly(DBO) segments. Debenzylation of 2 provided an amphiphilic block copolymer ( 3 ) consisting of hydrophilic (1→6)-α-D -glucopyranan (dextran) and hydrophobic poly(DBO) [(1→6)-linked polysaccharide skeleton] segments. Block copolymer 3 is soluble in dimethyl sulfoxide and swells in water and chloroform.     

Synthesis of block copolysaccharides by ring-opening polymerization of anhydro sugar derivatives

Ring-opening polymerization of anhtydro sugar derivatives was carried out with Lewis acid catalysts to produce block copolysaccharides. Polymerization of 1,4-anhydro-2,3-diO-tert-butyldimethylsilyl-α-D -ribopyranose (ADSR) with boron trifluoride etherate proceeded linearly and rapidly within 1 h to give silylated 1,5-α-D -ribofuranan in almost quantitative yield. Although the molecular weight distribution of the polymers was not narrow (M?_w/M?_n = 1.61 ～ 1.73), the relationship between monomer conversion and number-average molecular weight was linear, indicating livingness of the ring-opening polymerization. Thus, an AB block copolysaccharide composed of two different polysaccharide chains was synthesized for the first time in the two-stage polymerization of ADSR and 1,4-anhydro-2,3-di-O-benzyl-α-D -ribopyranose (ADBR) at ?40°C. Block copolysaccharides having different stereoregular monomeric units (i.e., ribopyranosidic and ribofuranosidic units) were obtained by block copolymerization of 1,4-anhydro-2,3-O-benzylidene-α-D -ribopyranose (ABRP) and ADBR. In addition, a block heteropolysaccharide consisting of (1 → 5)-α-D -xylofuranan and (1 → 5)-α-D -ribofuranan was prepared from 1,4-anhydro-2,3-di-O-tert-butyldimethylsilyl-α-D -xylopyranose (ADSX) and ADBR by making use of this polymerization technique. The GPC curves of block copolymers shifted toward the higher molecular weight region, maintaining the molecular weight distributions of the corresponding homopolymers in the first stage of polymerization. The number-average degree of polymerization of the polyADSR-block-polyADBR was estimated to be 113 for ADSR and 221 for ADBR unit. The ¹³C NMR spectra of the resulting block copolymers were different from those of the random copolymers.     

31P and 19F NMR spectroscopic studies on ring-opening polymerization of 1,6-anhydro-2,3,4-tri-O-benzyl-β-D-glucopyranose by PF5 catalyst

In order to elucidate the catalytic behavior of phosphorus pentafluoride in the polymerization of anhydro sugars, ¹³P and ¹⁹F NMR spectra were measured on a reaction mixture of 1,6-anhydro-2,3,4-tri-O-benzyl-β-D -glucopyranose (LGTBE) and PF₅ with different mole ratios in a temperature range of ?40 to ?80°C. In the ³¹P NMR spectrum measured at low temperatures, there was a total of 16 peaks, which consisted of a broad quintet, a septet, and a sharp quartet, being assigned to the PF₄O-group, to PF, and to POF₃, respectively. These fluoro compounds were also determined by the ¹⁹F NMR spectrum of the reaction mixture. The concentration of PF ions was found to correspond to that of oxonium ions, which are assumed to be actual propagating species, by determining both the concentration of PF from ¹⁹F NMR spectrum and the degree of polymerization of 2,3,4-tri-O-benzyl-α-D -glucopyranan obtained. Formation of the PF₅: LGTBE complex was observed from the ³¹P NMR spectrum of the polymerization system at ?80°C, which exhibits a broad sextet as well as absorptions due to POF₃, PF₄O–, and PF. To confirm the PF₅:LGTBE complex, the NMR measurement of the PF₅: tetrahydropyran complex was carried out. A polymerization mechanism of LGTBE by PF₅ catalyst is discussed on the basis of the NMR measurement of the polymerization system.     

Synthesis and free radical ring-opening polymerization of 2-methylene-4-phenyl-1,3-dioxolane

The cyclic ketene acetal, 2-methylene-4-phenyl-1,3-dioxolane ( 3 ), was shown to undergo free radical ring-opening polymerization to produce the polyester, poly[γ-(β-phenyl)butyrolactone]. The monomer 3 was synthesized by an acetal exchange reaction of chloroacetaldehyde dimethyl acetal with styrene glycol in an 87% yield followed by dehydrochlorination of the resulting cis and trans-2-chloromethyl-4-phenyl-1,3-dioxolane ( 2 ) with potassium tert-butoxide in tert-butyl alcohol in a 70% yield. 3 was shown to undergo essentially quantitative free radical ring-opening at all temperatures from 60–150°C and also nearly complete regioselective ring-opening with cleavage to give the more highly stable secondary benzyl free radical. Even in free radical copolymerization with styrene, methyl methacrylate, vinyl acetate, or 4-vinylpyridine, 3 gives essentially complete ring opening to introduce an ester groups into the backbone of the addition copolymer. The structures of the polymers were established by elemental analysis and ¹H and ¹³C NMR spectroscopy.     

Synthesis of 2,3,4-tri-O-benzyl-[1→6]-α-D-glucopyranan and [1→6]-α-D-glucopyranan with high molecular weight by polymerization of 1,6-anhydro-2,3,4-tri-O-benzyl-β-D-glucopyranose

The polymerization mechanism of 1,6-anhydro-2,3,4-tri-O-benzyl-β-D -glucopyranose ( 1 ) was investigated in order to synthesize 2,3,4-tri-O-benzyl-[1→6]-α-D -glucopyranan ( 2a ) and [1→6]-α-D -glucopyranan ( 2b ) (dextran) with high molecular weight. It was found that the optimum polymerization time to obtain high molecular weights was 40min when the monomer was polymerized in methylene chloride at ?60°C. Stereoregular 2a with a \documentclass{article}\pagestyle{empty}\begin{document}$ \overline {DP} _{\rm n} $ of 1800 (M?_n = 777000), which was about twice as high as the highest \documentclass{article}\pagestyle{empty}\begin{document}$ \overline {DP} _{\rm n} $ previously reported, was obtained in 77% yield by polymerizing the monomer with 0.8 mole-% PF₅ as catalyst applying a monomer-to-solvent weight/volume ratio of 50%. 2a with a high molecular weight was debenzylated to give 2b with a \documentclass{article}\pagestyle{empty}\begin{document}$ \overline {DP} _{\rm n} $ of 446 (M?_n = 72300). The α-stereospecificity and the solid state of the synthetic dextran were investigated by means of optical rotation, NMR spectroscopy, and X-ray diffraction pattern.     

Specific effect of antimony(V) containing initiators on the cationic copolymerization of 1,3-dioxolane with 5-methyl-2,3-dihydro-2-furanone

The copolymerization of 1,3-dioxolane ( 1 ) with 5-methyl-2,3-dihydro-2-furanone ( 2 ) was carried out in dichloromethane and nitrobenzene by use of triethyloxonium hexachloroantimonate, triethyloxonium hexafluoroantimonate, antimony pentachloride, antimony trichloride, and tin tetrachloride as initiators. The microstructures of the copolymers were analysed by means of ¹H-NMR, showing that monomer 2 was incorporated into the copolymer chain by the ring-opening reaction as well as by the ?normal”? vinyl addition, when triethyloxonium hexachloroantimonate, triethyloxonium hexafluoroantimonate, and antimony pentachloride were used. On the basis of NMR and IR studies on the complexation of Lewis acids with γ-lactones, it was concluded that the prominent effect of the initiators observed in the copolymerization of 1 with 2 was mainly attributable to the coordination between the initiator and the γ-lactone ring of monomer 2 .     

Ring-opening copolymerization of anhydroalditols with tetrahydrofuran

By ring-opening copolymerization of 1,4-anhydro-2,3-di-O-ethyl-D-erythritol (cis-3,4-diethoxyoxolane, 1 ) or 1,4:2,5:3,6-trianhydro-D-mannitol ( 3 ) with tetrahydrofuran carbohydratecontaining copolyether polyols were obtained. Using trifluoromethanesulfonic acid as catalyst the molecular weights were in a range from M?_w = 13 000 up to 25 000 with about 10% of carbohydrate constituent. The novel copolyethers were studied by polymer analytical procedures, their structures 4 and 5 tentatively assigned and compared to the homopolymerization products of the monomers. The present procedure features an approach to novel partially functionalized high molecular weight copolymer polyols based on carbohydrate-derived materials.     

Polymerization of cyclic monomers, 3. Synthesis,radical and cationic polymerization of bicyclic 2-methylene-1,3-dioxepanes

New bicyclic 2-methylene-1,3-dioxepanes, were synthesized starting from 2-bromomethyl-5,6-dihydroxy-1,3-dioxepanes. The structure of the 2-methylene-1,3-dioxepanes was confirmed by elemental analysis, IR, ¹H NMR and ¹³C NMR spectroscopy. Radical polymerization of 2-methylene-1,3-dioxepanes in bulk with 2,2′-azoisobutyronitrile (AIBN) and di-tert-butyl peroxide (DtBPO), respectively, gives highly viscous polymers. The polymerization of liquid monomers is accompanied by negative volume changes. The spectroscopic investigations of the formed polymers show that 2-methylene-1,3-dioxepanes undergo primarily radical ring-opening polymerization, whereas the cationic photopolymerization is mainly a vinyl polymerization.     

The cyclo-copolymerization of diallyl compounds and sulfur dioxide, 5. Copolymerization of some 4-substituted 1,6-heptadiene derivatives with sulfur dioxide

Copolymers of sulfur dioxide with N-substituted 4-(1,6-heptadiene-4-yl)pyridinium chlorides and bromides ( 1 ) and N-substituted 4-(3-butenyl)pyridinium chlorides and bromides, and some other 1,6-heptadiene derivatives 3 substituted in 4-position were prepared. The effects of the copolymerization conditions on the conversions and viscosities of the copolymers were studied and their structures by elemental analyses, IR and ¹H NMR spectroscopy. The thermal stabilities of the copolymers were also examined.     

Synthesis of 3-amino-ribofuranans having 1,5-α and -β structures by selective ring-opening polymerization of a 1,4-anhydro-3-azido-3-deoxy-α-D-ribopyranose derivative

Ring-opening polymerization of a new anhydro ribose-type monomer, 1,4-anhydro-3-azido-3-deoxy-2-O-tert-butyldimethylsilyl-α-D -ribopyranose (A3ASR), was investigated. The monomer was synthesized from 1,4-anhyro-α-D -xylopyranose by three steps comprising Walden inversion at the C3 position into ribose configuration. Ring-opening polymerization of A3ASR by Lewis acid catalysts such as boron trifluoride etherate and stannic chloride gave a stereoregular 3-azido-3-deoxy-2-O-tert-butyldimethylsilyl-(1→5)-α-D -ribofuranan having specific rotations of +246 ～ +271 deg · dm^?1 · g^?1 · cm³ and number-average molecular weights of 18,7 × 10³ ～ 25,1 × 10³. When the polymerization was carried out by antimony pentachloride at 0°C, the resulting polymer exhibited a negative specific rotation of ?6 deg · dm^?1 · g^?1 · cm³ and the C1 absorption in the ¹³C NMR spectrum shifted downfield to 107,5 ppm, suggesting that the polymer might consist of 1,5-β furanosidic unit. The reduction of the azido group of the 1,5-α and 1,5-β furanosidic polymers into amino group and subsequent desilylation gave 3-amino-3-deoxy-(1→5)-α- and -β-D -ribofuranans, respectively. In addition, copolymerization of A3ASR with 1,4-anhydro-2,3-di-O-tert-butyldimethylsilyl-α-D -ribopyranose (ADSR) in various feeds was performed by boron trifluoride etherate as catalyst to give copolymers with different monomeric components. The structural analysis of the homopolymers and copolymers was examined by means of ¹H and ¹³C NMR spectroscopies, IR spectroscopy, and optical rotation.     

Effect of ethyl benzoate on the microstructure distributions of olefin homopolymers and copolymers prepared with supported titanium catalyst

The microstructure distributions of ethylene-propene(EP) copolymers and propene homopolymers prepared with supported titanium catalyst were analyzed by ¹³C NMR spectroscopy. A two-site model with an isospecific site and a non-stereospecific site was used to describe the stereospecific polymerization of propene. A second two-site model with individual r₁r₂ = 1 was applied to the analysis of the ethylene-propene copolymerization. The addition of an external base, ethyl benzoate (EB), alters the relative concentrations of catalytic sites. Based on the comparison of the results from the homopolymers and copolymers prepared under different EB concentrations, the correlations between the stereospecificity and the activity toward the monomers were established: the isospecific site produces the copolymer with lower ethylene content; the non-stereospecific site gives the copolymer with higher ethylene content.     

13C NMR characterization of ethylene oxide/epichlorohydrin copolymer

The ¹³C NMR spectra of ethylene oxide/epichlorohydrin copolymers are fully assigned. Information available includes copolymer composition, comonomer sequence distribution, and epichlorohydrin tacticity. The comonomer sequence distribution can be fitted to a two-component (Bernoullian/Bernoullian) statistical model.     

Thermodynamics of copolymerization of 1,3-dioxolane with 1,3-dioxepane and 1,3-dioxane

The equilibrium copolymerization of 1,3-dioxolane with 1,3-dioxepane in CH₂Cl₂ solution and with 1,3-dioxane without solvent is analyzed, and the equilibrium constants of homo- and cross-propagations are estimated and discussed. The corresponding thermodynamic parameters are calculated. The reported thermodynamic parameters of homopolymerization of 1,3-dioxane (ΔH_ss = ?3,1 kJ · mol^?1, ΔS_ss = ?35,5 J · mol^?1 · K^?1), were determined on the basis of the copolymerization data. Predictions of comonomer concentrations and microstructure of copolymers in the equilibrium copolymerization system are presented for any initial composition, on the basis of the determined equilibrium constants.     

13C NMR studies of ethene-norbornene copolymers: assignment of sequence distributions using 13C-enriched monomers and determination of the copolymerization parameters

Ethene and norbornene were copolymerized using metallocene catalysts that produce copolymers having isolated norbornene units or microblocks with a maximum of two norbornene units. The resonances of the norbornene C_5/6 and the ethene carbon atoms, which overlap extensively in the ¹³C NMR spectrum, were differentiated and assigned by comparing the ¹³C NMR spectra of the copolymers obtained from monomers having ¹³C at natural abundance with those prepared from feedstocks containing ¹³C₁-enriched ethene or ¹³C_5/6-enriched norbornene. The NMR analysis revealed that the chemical shifts of the norbornene C_5/6 carbon atoms are triad sensitive and those of the ethene carbon atoms are pentad sensitive. ¹³C NMR analysis of copolymers containing isolated norbornene units in various proportions allowed the resonances of the norbornene C_5/6 and the ethene carbon atoms to be assigned to the respective triads and pentads. The complete triad distributions of these copolymers determined in this way were used to calculate the copolymerization parameters for a representative metallocene catalyst.     

Copolymerization of 1,3-dienes with CpTiCl3-MAO. Some cases in which the mode of monomer coordination affects the copolymer structure

The following pairs of monomers were copolymerized using the catalyst system CpTiCl₃/methylaluminoxane (MAO): 1,3-butadiene/(E)-1,3-pentadiene, 1,3-butadiene/4-methyl-1,3-pentadiene and 4-methyl-1,3-pentadiene/(Z)-1,3-pentadiene. The copolymers were characterized by NMR and infrared examination. 4-Methyl-1,3-pentadiene/(Z)-1,3-pentadiene and 1,3-butadiene/(E)-1,3-pentadiene gave copolymers having a composition intermediate between that of an ideal and that of an alternating copolymer. 1,3-Butadiene/4-methyl-1,3-pentadiene gave block copolymers only. These results have been interpreted on the basis of a different mode of coordination of the monomers. The cis-η⁴ coordination is by far the most stable for 1,3-butadiene and (E)-1,3-pentadiene, while for (Z)-1,3-pentadiene and 4-methyl-1,3-pentadiene there is probably an equilibrium between the cis-η⁴ and trans-η² form. Both these forms are reactive in the case of (Z)-1,3-pentadiene, while only the trans-η² form is so in the case of 4-methyl-1,3-pentadiene.     

Ring-opening-closing alternating copolymerization of 2-methyl-2-oxazoline with N-methyldiacrylamide

This paper describes a new ring-opening-closing alternating copolymerization (ROCAC) of 2-methyl-2-oxazoline (five-membered cyclic imino ether, 1 ) with N-methyldiacrylamide ( 2 ). The reaction of a 1 : 1 monomer feed ratio proceeded without any added catalyst to give an alternating copolymer 3 having two structural units formed by ring-opening and ring-closing (cyclization). The structure of copolymer 3 was determined by ¹H, ¹³C NMR, and IR spectroscopies. The extent of cyclization was at most 65%. The copolymerization was reasonably explained by a mechanism of propagation via zwitterion intermediates.     

New hyperbranched poly(ether amide)s via nucleophilic ring opening of 2-oxazoline-containing monomers

An AB₂ monomer containing one oxazoline and two phenolic units was synthesized. The polymerization of the monomer 2-(3,5-dihydroxyphenyl)-1,3-oxazoline in N-methylcaprolactam resulted in a well-defined and fully soluble, high molar mass, hyperbranched polymer with etheramide structure. The hydrolysis of some oxazoline groups as side reaction limits the achieved molar mass when the polymerization is carried out in tetramethylene sulfone or in bulk. The polymers were characterized by one (1D) and two (2D) dimensional ¹H and ¹³C NMR spectroscopy which allowed to determine the degree of branching to be 50% as expected from statistics. DSC and TGA measurements revealed a glass transition temperature of 176°C and a decomposition onset of 330°C. The thermal ring-opening reaction was studied in situ by DSC measurements.     

New amphiphilic copolymers of N-phenylmaleimides and vinyl ethers: thermal properties,Langmuir and Langmuir-Blodgett films,gas permeation

Amphiphilic copolymers 1 a–1d were prepared by radical copolymerization of hydrophilic N-phenylmaleimide derivatives and lipophilic vinyl ethers in dichloromethane. Though the starting concentrations of the two monomers were always equimolar, none of the copolymers had a strictly alternating structure. Molecular weights were between 10⁴ and 9 · 10⁴. The copolymers prepared from ethyl 4-maleimidobenzoate ( 2a ) and isobutyl vinyl ether ( 3a ) (copolymer 1a ), and 2a and isooctyl vinyl ether ( 3b ) (copolymer 1b ) were thermally stable up to 300°C and showed glass transitions at about 150°C, while the copolymers prepared from 2a and octadecyl vinyl ether ( 3c ) (copolymer 1c ), and 4-maleimidobenzoic acid ( 2b ) and 3c (copolymer 1 d ) were considerably less stable. All copolymers formed stable, condensed monomolecular layers at the air-water interface, which could be transferred onto hydrophobic supports by the Langmuir-Blodgett (LB) technique. Up to the 20th dipping cycle, a Y-type deposition was found, while further dipping predominantly led to Z-type deposition. Nitrogen and oxygen permeabilities (p) were studied after depositing the LB films onto porous Celgard membranes. Permeability and selectivity were dependent on the nature of the alkyl substituent group of the polymer. Copolymer 1a with the isobutyl group showed higher permeabilities than copolymer 1c with the octadecyl group, but no selectivity. The copolymer with the small alkyl group showed no selectivity of oxygen over nitrogen (α = )P_O2/P_N2 while for the copolymer with the long alkyl chain the α-value was 1,3.     

Copolymerization of C-vinyltriazoles and C-vinyltetrazole with vinyl monomers

The copolymerizations of 4(5)-vinyl-1,2,3-triazole, 1-p-bromophenyl-4-vinyl-1,2,3-triazole and 2-methyl-5-vinyltetrazole with styrene, methyl methacrylate and vinyl acetate have been examined and the corresponding copolymerization parameters r₁, r₂ were evaluated. The reactivities Q of these monomers are lower than that of styrene contrarily to other C-vinylheterocyclic monomers; it is assumed that it results from a limited stabilization of the corresponding radicals. In the case of 4(5)-vinyl-1,2,3-triazole, copolymerizations carried out at different temperatures and varied monomer concentrations show that intermolecular monomer association (as evidenced by NMR and IR measurements) does neither affect the copolymer composition nor the internal monomer triad structure of the copolymer.