Anionic polymerization initiators containing protected functional groups. II

An organolithium reagent substituted with a primary amine-protecting group [i.e.,? N(TMS)₂] has been prepared and used to polymerize 1,3-butadiene and isoprene. A method is described for converting the resulting? N(TMS)₂-containing polydienes into? NH₂-containing polymers. Both ? N(TMS)₂- and ? NH₂-terminated polydienes have been characterized with regard to microstructure, M _n, and M _w/M _n data, as well as qualitative and quantitative end-group analyses. The described preparative procedures represent a convenient route to the elusive primary amine-terminated polydienes.     

Anionic living polymerization of styrenes containing electron-withdrawing groups

Six styrene derivatives containing electron-withdrawing groups were synthesized and polymerized with anionic initiators in THF to afford stable anionic living polymers. The electron-withdrawing substituents are N,N-dialkylamide(1), N-alkylimino(2), oxazoline(3), tert-butyl ester(4), N,N-dialkylsulfonamide(5) and cyano(6) moieties. The polymers obtained have predictable molecular weights and narrow molecular weight distributions. The respective postpolymerizations proceeded with quantitative efficiency indicating that each polymer chain end retained the propagating reactivity. However, the resulting living polymers could not initiate the polymerizations of styrene and isoprene. On the other hand, the styrene derivatives(5 and 6) were polymerized with weak nucleophilic initiators, such as living polymer of tert-butyl methacrylate. These results suggest that the electron-withdrawing groups stabilize the living ends and also activate the respective monomers for anionic polymerization. The substitution effect reflects on the ¹³C NMR chemical shift of β-carbon of each vinyl group. The signal of the β-carbon appeared at lower magnetic field than that of styrene indicating electron deficiency on the carbon-carbon double bond of these monomers.     

Free radical ring-opening polymerization and its use to make biodegradable polymers and functionally terminated oligomers

Since a carbon-oxygen double bond is considerably more stable than a carbon-carbon double bond, it has been possible to use this driving force to promote free radical ring-opening polymerization of unsaturated heterocyclic compounds. This process, for the first time, has permitted the introduction of functional groups, such as esters, amides and carbonates, into the backbone of addition polymers. Hydrolysis of the copolymers with common monomers produced oligomers capped with hydroxyl, amino or carboxylic acid groups. The presence of an ester group in a copolymer, such as in a copolymer of ethylene, render the copolymer biodegradable.     

Anionic graft polymerization of methyl acrylate to protein functional groups

Graft polymerization of methyl acrylate to functional groups in proteins was studied with model compounds and with whole gluten proteins. Polymerization was carried out in the presence of sodium hydride or sodium in dimethyl sulfoxide. Initiation proceeds by an anionic mechanism, and the rate-determining step is the production of the initially formed carbanion. The rate of disappearance of methyl acrylate was followed via gas chromatography. Amino acid analyses indicated that the functional groups of the amino acids, as well as the peptide bonds, were acting as the initiation sites in proteins. Reaction rates of the functional groups were determined on model compounds in the presence of sodium and sodium hydride. With both the model compounds and the proteins, polymerization was initially rapid and then leveled off, although rates depended on the concentration of activator and acrylate. Methoxyl group analyses of modified model compounds and proteins indicated that from 5 to 10 methyl acrylate residues were introduced per reactive site.     

Telechelic diene prepolymers. IV: Anionic polymerization studies

The preparation and characterization of functionally terminated polybutadienes by an anionic polymerization technique is described. Prepolymers possessing hydroxyl end-groups were synthesized via vacuum-line methods. Characterization was completed through endgroup, functionality, molecular weight, molecular weight distribution, and microstructural analyses. Emphasis was placed on the reproducibility in the properties of the prepolymers, particularly in their functionality.     

Anionic graft copolymerization of diene polymers with vinyl monomers

A mixture of homopolymer and graft copolymer was obtained by adding the monomer at 0°C to the polylithiodiene solution. Styrene, methyl methacrylate, and acrylonitrile were used as the monomers. Polylithiodienes were prepared by the metalation of diene polymers, i.e., polybutadiene or polyisoprene, with the use of n-butyllithium in the presence of a tertiary amine (N,N,N′,N′-tetramethylethylenediamine) in n-heptane. The graft copolymers were separated by solvent extraction and were confirmed by turbidimetric titration and elementary analysis. Oxidation of the polybutadiene–styrene grafts revealed that the molecular weight of the side chains was the same as the molecular weight of the free polystyrene formed. The grafting efficiency and grafting percentage were studied for polybutadiene–styrene graft copolymers prepared under various conditions.     

Novel functional initiators for oxazoline polymerization

The initiating behavior of the functional tosylates 1 – 4 and triflates 5 and 6 for the cationic ring‐opening polymerization of 2‐methyl‐1,3‐oxazoline was investigated. The emphasis was directed at tosylates and triflates with 2,2‐dimethyl‐1,3‐dioxolane‐, 2,3‐epoxypropyl‐, 2,3‐didodecanoyl‐glycerol‐, and cholest‐5‐en‐moieties that allow the construction of amphiphilic polyoxazoline conjugates. The tosylates were prepared by a simple reaction of the corresponding alcohols with p‐toluenesulfonyl chloride, whereas the preparation of the corresponding triflates required low temperature and the use of 2,6‐di‐tert‐butylpyridine as a sterically hindered base. Among the initiators tested, 2,2‐dimethyl‐(4‐trifluoromethanesulfonyloxymethyl)‐1,3‐dioxolane 6 gave the best results in respect to molecular weight and polydispersity. Starting from the corresponding functional oxazoline polymers obtained with 6 as an initiator, amphiphilic lipid‐polyoxazoline conjugates with a diacylglycerol backbone could be prepared. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2821–2831, 2001     

Studies on polymers containing functional groups. VI. Kinetics of the polymerization and copolymerization behaviors of o-hydroxystyrene

Some kinetic studies were made of the homopolymerization of o-hydroxystyrene and its copolymerization behavior with styrene and methyl methacrylate in tetrahydrofuran using azobisisobutyronitrile as initiator were done. The rate of polymerization experimentally obtained is given by R_p = K[M][I]^0.72. Accordingly, it is likely that the growing chain radicals are terminated not only by mutual termination but also by a chain-transfer mechanism, the latter occupying a considerable portion. The latter is mostly attributed to the transfer to monomer, i.e., C_m for o-hydroxystyrene was 1.3 × 10^?2. Some transfer mechanisms were assumed, although it is difficult to elucidate the mechanism in detail, owing to its complexity. Effects of solvent on the rate of polymerization were examined, dioxane, methyl ethyl ketone, ethanol, and tetrahydrofuran being used. However, no differences were found among the solvents. The apparent activation energy of polymerization was found to be 21.5 kcal./mole. Monomer reactivity ratios and Alfrey-Price Q–e values for o-hydroxystyrene were determined. The Q–e values (Q = 1.41, e = ?1.13) are rather similar to those of p-methoxystyrene. Thus, the e value for o-hydroxystyrene is more negative than that for styrene.     

Studies on polymers containing functional groups. III. Charge-transfer interaction between quinone and aza polymers

Absorption maxima and equilibrium constants for charge-transfer complexes between quinone and aza polymers, such as poly-2-vinylpyridine, poly-4-vinylpyridine, poly-2-methyl-5-vinylpyridine, and poly-N-dimethylaminomethylacrylamide, were determined spectrophotometrically. For comparison, those for charge-transfer complexes between quinone and aza compounds, such as pyridine, methyl-substituted pyridines, quinoline, triethylamine, and dimethylaniline were also presented. It was found that the equilibrium constants for polymer complexes are always larger than those for the corresponding monomer complexes, while the time required for attaining the equilibrium was longer for polymer complexes than for monomer complexes. In the interaction between quinone and poly-N-dimethylaminomethylacrylamide, two absorption maxima which gradually shifted towards each other were observed. The same phenomenon was found in the interaction between quinone and the corresponding monomer, triethylamine.     

Plasma polymers containing sulfonate groups

Modification of plasma-polymers prepared from phenylsilane with sulfur trioxide was investigated by FT/IR spectroscopy and ESCA. The sulfonation of phenyl groups in the plasma-polymers occurred rapidly within 1 min when exposed to SO₃ gas. The S/C and O/C atomic ratios determined by ESCA for the modified polymers were 0.13₈ and 0.41₈, respectively. The sulfonation made the plasma-polymers electrically conductive. The conductivity was sensitive to moist atmosphere. The logarithm of the impedance at 120 Hz decreased linearly with increasing the relative humidity. The plasma-films containing sulfonate groups may be a new material for moisture sensor devices.     

Crosslinked polymers containing adamantane groups

Diglycidyl ethers of 1,3-bis-(p-hydroxyphenyl)adamantane (BHPA) and 3,3'-bis-(p-hydroxyphenyl)-1,1'-biadamantane (BHPBA) were prepared and condensed with m-phenylenediamine and methyl tetrahydrophthalic anhydride to give polymers with good high temperature mechanical properties and good oxidative stability. These bisphenols were also condensed with formaldehyde to give phenolic resins containing adamantane moieties.     

Triptycene‐containing polyetherolefins via acyclic diene metathesis polymerization

Several new triptycene‐containing polyetherolefins were synthesized via acyclic diene metathesis (ADMET) polymerization. The well‐established mechanism, high selectivity and specificity, mild reaction conditions, and well‐defined end‐groups make the ADMET polymerization a good choice for studying systematic variations in polymer structure. Two types of triptycene‐based monomer with varying connectivities were used in the synthesis of homopolymers, block copolymers, and random copolymers. In this way, the influence of the triptycene architecture and concentration in the polymer backbone on the thermal behavior of the polymers was studied. Inclusion of increasing amounts of triptycene were found to increase the glass transition temperature, from ?44 °C in polyoctenamer to 59 °C in one of the hydrogenated triptycene homopolymers ( H‐PT2 ). Varying the amounts and orientations of triptycene was found to increase the stiffness ( H‐PT1 ), toughness ( PT1₁‐b‐PO₁ ) and ductility ( PT1₁‐ran‐PO₃ ) of the polymer at room temperature. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Cyclo- and cyclized diene polymers. XII. Cationic polymerization of isoprene

Polymerization of isoprene with Lewis acids in n-heptane is a process leading to a quasiequilibrium which is characterized by very low conversions. Polymerization rates in aromatic solvents are much higher due to extensive chain transfer with solvent with regeneration of the original active centers. The rate of monomer disappearance in benzene or toluene when aluminum bromide is the catalyst is second order with respect to monomer concentration. The reaction order with respect to the catalyst depends on the reaction conditions; at constant monomer concentration it is approximately one. Polymerization rates in halogenated solvents with the use of syringe techniques are much higher than those in aromatic solvents. Polymers obtained with various cationic catalysts ranged from oils to white powders having molecular weights up to more than 100,000 depending on reaction conditions. All polymers exhibited infrared spectra characteristic of cyclopolydienes, and the content of linear structures usually did not exceed 20%, irrespective of the nature of the catalyst or solvent. In solvents of higher polarity, such as o-dichlorobenzene, more linear structures were detected. Among residual linear forms the trans-1,4 addition was found to prevail. Residual unsaturation in polymers did not exceed 30%.     

Ferrocene-containing polymers synthesized by acyclic diene metathesis (ADMET) polymerization

Herein we reported that ferrocene-containing polymers could be synthesized via acyclic diene metathesis(ADMET) polymerization of ferrocene-containing bis-styryl monomers. The all-trans-configured vinylene bonds of stilbene segment were proven by means of 13C-NMR, 1H-NMR, MALDI-TOF mass spectrometry and FTIR. Poly(1) showed maxima for absorption at 320 nm and emission at 430 nm which are structurally very similar to trans-stilbene, but 24 and 16 nm red shifted respectively. CIE chromaticity diagram shows that emission color could be adjusted by controlling the molecular weight. The polymer showed excellent solubility in common organic solvents and good thermal stability evidenced by TGA and DSC. The results of CV suggested the polymer possessed noninteracting metal centers which was confirmed by a reversible one-electron redox wave observed for the polymer.     

Gamma-ray polymerization of phospholipids having diene or triene groups as liposomes

Small unilamellar liposomes were prepared in an aqueous medium by the sonication of phospholipids containing diene or triene groups in their hydrocarbon acyl chains. These liposomes were polymerized by gamma-ray irradiation. Conversion of polymerization was successively followed by UV spectrometry. Diene-type lipid liposomes were revealed for which a gamma-ray dose of 0.8 Mrad was required for complete polymerization and which were polymerized more easily than triene-type lipid liposomes. Triene-type lipids required 2.3 Mrad gamma ray to polymerize them completely. Contrary to UV-irradiation polymerization, there was no concentration dependence on the polymerization. Structure of the polymerized liposomes were confirmed by electron microscopy as small unilamellar liposomes. Study on the leakage of fluorescein from inner aqueous phase of the polymerized liposomes revealed that polymerized triene-type liposomes were relatively more stable than the polymerized diene-type liposomes.     

Studies on polymers containing functional groups. II. Polymerization behavior of o-hydroxystyrene

The polymerization behavior of o-hydroxystyrene with free-radical and cationic initiators and without an initiator was examined. The structures thus obtained were estimated. Although polymerization behavior of o-hydroxystyrene was rather complicated, according to the results, it appeared that each polymerization more or less might simultaneously follow the two types of mechanisms: normal vinyl polymerization and polymerization through the addition to benzene nuclei. The proportion of addition to benzene nuclei was considered to be highest in the polymerization with BF₃·(OEt)₂ and lowest in that with azobisisobutyronitrile. Degrees of polymerization of these polymers were low in all cases (42–82). Some brief experiments on copolymerization of o-hydroxystyrene were carried out.     

Organosilane polymers: Formable polymers containing reactive side groups

Formable organosilane polymers containing various reactive side groups were synthesized by hydrosilylation of unsaturated compounds containing reactive groups with poly(methylsilane) in the presence of platinum complexes. These polymers have appreciable solubility in common solvents, can be molded or cast into films or drawn into fibers, and are photoactive.     

Anionic polymerization of methacrylonitrile—II.: Polymerization with 1,1-diphenyl-n-hexyllithium and sec-butyllithium as initiators

The anionic polymerization of methacrylonitrile has been investigated at ?75° in toluene with 1,1-diphenyl-n-hexyllithium and sec-butyllithium as initiators. With both initiators, initiation was fast and no unreacted initiator was left. The efficiency was much higher for 1,1-diphenyl-n-hexyllithium than for sec-butyllithium probably for steric reasons. With both initiators, a second order dependence on initiator was found. To check that this is not an artifact resulting from measurements in a medium starting to gel at a point which is difficult to detect precisely, kinetic measurements were also carried out with 2-polystyryl-l,l-diphenylethyllithium as an initiator. Second order kinetics were again obtained; the propagation rate constants, taking into account the efficiencies of initiators, were the same within experimental error for all three initiators. Viscosity measurements performed on a methacrylonitrile “capped” 2-polystyryl-l,l-diphenylethyllithium initiator showed the living polymethacrylonitrile chains to be associated.     

Monomers and polymers with silicon-containing functional groups

The novel monomer, p-vinylphenoxy(trimethyl)silane, has been prepared and copolymerized with styrene. The hydrolysis of the copolymer in dioxan has been examined briefly. Monomers of the type p-CH₂CHC₆H₄SiMe₂R (RH, OMe, OEt, OPr, CH₂Cl and NMc₂) have been prepared, polymerized and the resulting polymers cross-linked by hydrolysis.