Equimolar “a2 + b4” polycondensations—Cyclic polyethers derived from 1,4‐dicyanotetrafluorobenzene and various diphenols

Dicyanotetrafluorobenzene was polycondensed with bisphenol‐P, bisphenol‐M, or 1,4‐bis(4‐hydroxyphenoxy)butane in DMF. Either K₂CO₃ and ethyldiisopropylamine (EDPA) or tetramethyl piperidine (TMPD) was used as catalysts and HF acceptors. Regardless of base and concentration, all polycondensations of bisphenol‐P or 1,4‐bis(4‐hydroxyphenoxy)butane yielded more or less crosslinked polyethers. In the case of bisphenol‐M, all polycondensations conducted with K₂CO₃ and 0.4, 0.2, or 0.1 M monomer concentrations resulted again in gelation. Gels were also obtained when polycondensations of 0.4 M monomer solutions were catalyzed with EDPA or TMPD. Yet, at a concentration of 0.2 M, the amines yielded completely soluble polyethers, which were characterized by elemental analyses, inherent viscosities, MALDI‐TOF mass spectrometry, and DSC measurements. The mass spectra revealed that the soluble polyethers mainly consisted of cycles containing two C? F bonds per repeat unit. Nearly quantitative substitution of the C? F groups with 4‐chlorothiophenol, 4‐bromophenol, 4‐aminophenol, and 4‐phenyl azophenol proved successful, so that a broad variety of multifunctional polyethers was obtained, but in the case of 4‐chloro thiophenol cleavage of the polyether chain also occurred. © 2007 Wiley Periodicals, Inc. JPolym Sci Part A: Polym Chem 46: 543–551, 2008     

Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectroscopic analysis of telechelic polythiourethanes obtained by the cationic ring‐opening polymerization of six‐membered cyclic thiourethane

A matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectroscopy analysis of polythiourethanes obtained by the cationic ring‐opening polymerization of a six‐membered cyclic thiourethane [3‐benzyltetrahydro‐1,3‐oxazine‐2‐thione (BTOT)] is described. A MALDI‐TOF mass spectrum of a polymer obtained by the polymerization of BTOT with boron trifluoride etherate (BF₃OEt₂) as the initiator in nitrobenzene at 50 °C for 24 h followed by an end‐capping reaction with diethyldithiocarbamic acid diethylammonium salt showed a series of well‐resolved signals that were assignable to polythiourethanes possessing an amino group at the initiating end and a diethyldithiocarbamate group at the terminating end. In comparison with the MALDI‐TOF mass spectra of polymers obtained by polymerization with trifluoromethanesulfonic acid or methyl trifluoromethanesulfonate, the plausible initiating species in the polymerization with BF₃OEt₂ was estimated to be a proton, which successively eliminated carbonyl sulfide to produce a secondary amine group at the initiating end. The secondary amine group in the obtained telechelic polymer was converted to a tertiary amine group by a reaction with benzyl bromide in the presence of triethylamine, and this was confirmed by MALDI‐TOF mass spectroscopy. Furthermore, a telechelic polymer with a pyrrole end group was successfully synthesized by the end‐capping reaction of the growing species in the polymerization of BTOT with sodium 1‐pyrrolecarbodithioate. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4281–4289, 2006     

Novel AB crosslinked polymer networks from telechelic 4‐vinylbenzyl carbamate terminated polyurethanes and different vinyl monomers

Novel AB crosslinked polymer (ABCP) networks were synthesized from telechelic 4‐vinylbenzyl carbamate terminated polyurethanes and monomers such as styrene, 4‐vinylpyridine, methyl methacrylate and butyl acrylate. Telechelic 4‐vinylbenzyl carbamate terminated polyurethanes were synthesized from polypropylene glycol‐based NCO‐terminated polyurethane and vinylbenzyl alcohol. Effect of changing the molecular weight of polypropylene glycol on the static and dynamic mechanical properties of ABCP networks from polyurethane‐polymethyl methacrylate was studied in detail. Dynamic mechanical thermal analysis results show that polymethyl methacrylate and polystyrene‐based ABCPs have good damping over a broad temperature range. ABCP networks prepared from 4‐vinylbenzyl carbamate terminated polyurethane and different monomers such as methyl methacrylate, butyl acrylate and styrene exhibit single tan δ_max value which implies excellent interlocking between the two polymers present in the ABCP networks. Static mechanical studies showed that methyl methacrylate and styrene‐based ABCP networks exhibit better tensile properties compared to other ABCP networks from butyl acrylate and 4‐vinyl pyridine monomers. Thermogravimetric analysis results revealed that the ABCP networks showed an improved thermal stability. Copyright © 2009 John Wiley & Sons, Ltd.     

Proton‐conductive polymer nanocomposite membranes prepared from telechelic fluorinated polymers containing perfluorosulfonic acid side chains

New classes of fluorinated polymer–polysilsesquioxane nanocomposites have been designed and synthesized. The synthesis method includes radical polymerization using the functional benzoyl peroxide initiator for the telechelic fluorinated polymers with perfluorosulfonic acids in the side chains and a subsequent in situ sol–gel condensation of the prepared triethoxylsilane‐terminated fluorinated polymers with oxide precursors. The telechelic polymer and nanocomposites have been carefully characterized by ¹H and ¹⁹F NMR, FTIR, TGA, and TEM. The ion‐exchange capacity (IEC), water uptake, the state of the absorbed water, and transport properties of the composite membranes have been extensively studied as a function of the content and structure of the fillers. Unlike the conventional Nafion/silica composites, the proton conductivity of the prepared membranes increases steadily with the addition of small amounts of the polysilsesquioxane fillers. In particular, the sulfopropylated polysilsesquioxane‐based nanocomposites display proton conductivities greater than Nafion. This is attributed to the presence of pendant sulfonic acids in the fillers, which increases IEC and offers continuous proton transport channels between the fillers and the polymer matrix. The methanol permeability of the prepared membranes has also been examined. Lower methanol permeability and higher electrochemical selectivity than those of Nafion have been demonstrated in the polysilsesquioxane‐based nanocomposites. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Hyperbranched cyclic and multicyclic polymers by “a2+b4” polycondensations

At first, theoretical aspects of “a₂+b₄” polycondensations (meaning polycondensations of difunctional and tetrafunctional monomers) are discussed and compared with what is known about “a₂+b₃” polycondensations. The following review of experimental results is subdivided into three sections. First, syntheses of hyperbranched polyethers and polyesters by polycondensations based on equimolar feed ratios will be reported. Second, kinetically controlled (i.e., irreversible) syntheses of multicyclic polymers using equifunctional feed ratios (i.e., a₂/b₄ ratios of 2:1) will be described. In the third section, syntheses of multicyclic polymers via thermodynamically controlled (reversible) “a₂+b₄” polycondensations will be discussed. Characteristic for these polycondensations are again equifunctional feed ratios and metal alkoxides as “a₂” or “b₄” monomers, which catalyze rapid equilibration reactions. Finally, potential applications of the new polymers will shortly be mentioned. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1971–1987, 2009     

Cyclic and branched functional polyesters derived from 5,5′,6,6′‐tetrahydroxy‐3,3,3′,3′‐tetramethyl spirobisindane and various dicarboxylic acids

Triethylamine‐promoted polycondensations of 5,5′,6,6′‐tetrahydroxy‐3,3, 3′,3′‐tetramethyl spirobisindane (TTSBI) and α,ω‐alkane dicarboxylic acid dichlorides were performed with equimolar feed ratios. Three different procedures were compared. At a TTSBI concentration of 0.05 mol/L, gelation was avoided, and soluble cyclic polyesters having two OH groups per repeat unit were isolated. These polyesters were characterized with ¹H NMR spectroscopy, MALDI‐TOF mass spectrometry, and SEC and DSC measurements. All polycondensations with sebacoyl chloride resulted in gelation, regardless of the procedure. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1699–1706, 2007     

Syntheses of multicyclic poly(ether sulfone)s from 5,5′,6,6′‐tetrahydroxy‐3,3,3′,3′‐tetramethyl spirobisindane and 4,4′‐bis(4‐chlorophenyl) sulfones

5,5′,6,6′‐Tetrahydroxy‐3,3,3′,3′‐tetramethyl spirobisindane (TTSBI) was polycondensed with 4,4′‐dichlorodiphenyl sulfone (DCDPS) or with 4,4′‐bis(4‐chlorophenyl sulfonyl) biphenyl (BCSBP) in DMSO. Concentration and feed ratio were optimized to avoid gelation and to obtain a maximum yield of multicyclic polyethers free of functional groups. Regardless of these reaction conditions, only low fractions of perfect multicycles were obtained from DCDPS apparently due to steric hindrance of ring closure. Under the same conditions high fractions of perfect multicycles were achieved with the longer and more flexible DCSBP. The reaction products were characterized by MALDI‐TOF mass spectrometry, ¹H‐NMR spectroscopy viscosity, and DSC measurements. Relatively low glass transition temperatures (T_gs ≈ 160–175 °C) were found. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3732–3739, 2008     

Poly(hydroxyisobutyrate) by ring‐opening polymerizations of 5,5‐dimethyl‐1,3,2‐dioxithiolan‐4‐one‐2‐oxide

α‐Hydroxyisobutyric acid anhydrosulfate HiBAS (5,5‐dimethyl‐1,3,2‐dioxithiolan‐4‐one‐2‐oxide) was polymerized under various reaction conditions and the solid reaction products were characterized by ¹H NMR spectroscopy, MALDI‐TOF mass spectrometry (MT m.s.), fast atom bombardment mass spectrometry (FAB m.s.), viscosity, and SEC measurements. Thermal polymerizations at 100 °C mainly yielded cyclic oligo polyesters presumably resulting from a zwitterionic polymerization. Cycles were also detected when pyridine was used as catalyst at 20 °C. When triethylamine was used as catalyst traces of H₂O played the role of initiators. Benzyl alcohol initiated the polymerization of HiBAS at 100 °C and yielded a polyester terminated by one benzylester and one OH endgroup. The SEC measurements indicated that all samples possess relatively low molar masses with number–average molecular weights ≤ 10,000 Da (in contrast to the literature data). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6229–6237, 2008     

Synthesis and characterization of a helical step‐ladder polyarylene

A helical step‐ladder polyarylene incorporating chiral (R)‐2,2′‐dioctoxy‐1,1′‐binaphthyl units was synthesized for the first time. The first step involved the preparation of a precursor poly(arylene ketone) via a palladium‐mediated Suzuki‐type cross‐coupling reaction with the aid of microwave heating. Two polymer‐analog reaction steps, the reduction of the keto groups to tertiary alcohol functionalities and subsequent intramolecular Friedel–Crafts cyclization, gave a step‐ladder polymer ( 6 ) in good yields with reasonable mean average molecular weights greater than 13,000. The regioselective cyclization pattern in the α position of the naphthalene core was confirmed by a comparison of the NMR data of the polymer with those of the corresponding model ladder oligomers, 12 and 13 , and also a single‐crystal structure of 13 . The optical spectra of the oligomers and polymers indicated that there was little electronic interaction across the binaphthyl units. The circular dichroism spectrum of 6 exhibited a strong bisignate Cotton effect in the π–π* absorption region of the planar chromophores, which reflected the strong exciton coupling within the helical polymer chain. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5533–5545, 2006     

Cleavable multiblock copolymer synthesized by ring‐opening metathesis copolymerization of cyclooctene and macrocyclic olefin and its hydrolysis to give carboxyl‐telechelic polymer

A novel cleavable multiblock copolymer was synthesized by ring‐opening metathesis polymerization (ROMP) of cyclooctene (COE) and a flexible 27‐membered macrocyclic olefin (MCO), which is acted as the spacer to collect the polymer structure block by block. MCO 2 was prepared via ring‐closing metathesis of the long chain alkyldiene, and then 2 was well‐ conducted ROMP with COE to provide the multiblock copolymer [Poly(COE)‐ 2 ]_m consisting of homo‐Poly(COE) blocks and ring‐opened 2 segments with different molecular weights (M_n = 30.0 – 249.6 × 10³) and polydispersity index (PDI) within 1.45–1.67 as variation of the feed ratio of COE to 2 . The multiblock copolymer chain containing weak ester linkage can be cleaved under alkali condition to afford the carboxyl‐telechelic Poly(COE) blocks with much lower molecular weights (M_n,h = 3.6–35.7 × 10³) and slight higher PDIs (1.65–1.88). The average block number on multiblock copolymer chain was obtained from the ratio of M_n to M_n,h and was reached up to the value of 7–16. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 380–388, 2010     

Antimicrobial polymers containing melamine derivatives. II. Biocidal polymers derived from 2‐vinyl‐4,6‐diamino‐1,3,5‐triazine

Poly(2‐vinyl‐4,6‐diamino‐1,3,5‐triazine) (PVDAT) and a series of poly(styrene‐co‐2‐vinyl‐4,6‐diamino‐1,3,5‐triazine) (PS‐co‐VDAT) copolymers were synthesized via conventional free‐radical polymerizations. The polymer structures were confirmed by Fourier transform infrared, NMR, and elemental analysis. The molecular weights were determined by gel permeation chromatography studies, and the thermal properties were characterized by differential scanning calorimetry and thermogravimetric analysis. After treatment with chlorine bleach, PVDAT and PS‐co‐VDAT provided potent antimicrobial functions against multidrug‐resistant Gram‐negative and Gram‐positive bacteria. The antimicrobial functions were durable for longer than 3 months and rechargeable for more than 50 times. The structure–property relationship of the polymers was further discussed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4089–4098, 2005     

Multifunctional materials based on polyazomethines derived from 2,5‐dihydroxy‐1,4‐benzoquinone and siloxane diamines

New polyazomethines have been synthesized by the reaction between 2,5‐dihydroxy‐1,4‐benzoquinone and siloxane diamines differing by the siloxane sequence length. A dimer has also been prepared as a model compound. The products were characterized by spectral (FTIR and ¹H‐NMR) and elemental analyses, GPC, viscosity measurements, solubility tests, and transmission electron microscopy (TEM). The different properties have been investigated by adequate techniques: thermal (DSC and TGA), spectral (UV–vis and fluorescence spectroscopy), redox (Differential Pulse Voltammetry). pH‐sensitivity and metal complexing ability were also evaluated. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1862–1872, 2008     

Multicyclic polyethers by the polycondensation of 1,2‐ or 1,3‐dicyanotetrafluorobenzene with flexible diphenols

1,2‐Dicyanotetrafluorobenzene (1,2‐DCTB) was polycondensed with various flexible diphenols in a molar ratio of 1:2, and experimental parameters such as the concentration and temperature were varied. Certain diphenols allowed a complete substitution of all C? F bonds, so perfect multicyclic polyethers (B_nCN, where B stands for bridge units, C represents cycles, and N is the degree of polymerization) were the main reaction products. Despite complete conversion, gelation was avoidable under optimized reaction conditions. However, in the case of 1,3‐dicyanotetrafluorobenzene (1,3‐DCTB), complete tetrasubstitution was not feasible with a feed ratio of 1:2. Yet, because of the inductive and mesomeric electronic interactions of all substituents in 1,3‐DCTB, the three C? F groups in the ortho position with respect to the cyano groups were significantly more reactive than the fourth C? F bond. Therefore, polycondensations with diphenols in a 3:2 feed ratio showed a relatively clean course, yielding soluble multicycles of structure B_{n /2}CN. All the multicyclic polyethers were amorphous and possessed molar mass distributions with polydispersities greater than 2. Heating with Cu²⁺ salts caused crosslinking of the multicycles derived from 1,2‐DCTB because of the formation of phthalocyanine complexes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5546–5556, 2006     

Low‐oxidation‐potential conducting polymers derived from 3,4‐ethylenedioxythiophene and dialkoxybenzenes

Monomers derived from 3,4‐ethylenedioxythiophene and phenylenes with branched or oligomeric ether dialkoxy substituents were prepared with the Negishi coupling technique. Electrooxidative polymerization led to the corresponding dialkoxy‐substituted 3,4‐ethylenedioxythiophene–phenylene polymers, with extremely low oxidation potentials (E_1/2,p = ?0.16 to ?0.50 V vs Ag/Ag⁺) due to the highly electron‐rich nature of these materials. The polymers were electrochromic, reversibly switching from red to blue upon oxidation, with bandgaps at about 2 eV. The electrochemical behavior of the oligomeric ether‐substituted polymer was investigated in the presence of different metal ions. Films of the polymer exhibited electrochemical recognition for several alkali and alkaline‐earth cations with selectivity in the order Li⁺ > Ba²⁺ > Na⁺ > Mg²⁺. Cyclic voltammetry showed a decrease in the oxidation potential and an improvement in the definition of the voltammetric response, as well as an increase in the overall electroactivity of the polymer films when the concentration of the cations in the medium was increased. These results are discussed in terms of the electrostatic interactions between the complexed cation and the redox center, as well as the diffusion of the ionic species into the polymer matrix. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2164–2178, 2001     

Norbornyl benzocyclobutene ladder polymers: Conformation and microporosity

Shape-persistent contorted ladder polymers are an intriguing and unusual class of polymers. Using catalytic arene-norbornene annulation (CANAL) polymerization and with norbornadiene and dibromoarenes as monomers, we synthesized a series of ladder polymers with fused norbornyl benzocyclobutene backbones and varied conformations. A diaryl spiro-orthocarbonate monomer was used to reorient the ladder backbone perpendicularly to induce three-dimensional kinks, and a p-dibromo-xylene comonomer was used to statistically vary the distance between the spirocyclic kinks in the ladder backbone. Norbornyl benzocyclobutene ladder polymers with no spirocyclic backbone twists possess much more compact conformations than ladder polymers with frequent spirocyclic backbone twists in solution. While spirocyclic twists in the polymer backbone had minor effects on the surface area and microporosity, incorporation of rotatable single bonds in the repeat unit significantly decreased both the surface area and pore volume. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3075–3081     

Cyclic poly(pyridine ether)s by the polycondensation of 2,6‐difluoropyridine with various diphenols

The bistrimethylsilyl derivatives of six different diphenols were polycondensed with 2,6‐difluoropyridine in N‐methylpyrrolidone in the presence of K₂CO₃. On the basis of previous studies, the reaction conditions were optimized for almost quantitative conversions. The feed ratio was systematically varied to optimize the molecular weight. A 2 mol % excess of 2,6‐difluoropyridine was needed to obtain maximum molecular weights. In the matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectra of the optimized polyethers, only cycles were found (detectable up to 5000 Da). Obviously, the relatively low molecular weights obtained under optimized conditions resulted from a limitation of the chain growth by cyclization, indicating a high cyclization tendency for poly(pyridine ether)s. The size exclusion chromatography measurements not only proved low molecular weights but also demonstrated the existence of bimodal mass distributions and high polydispersities. Protonation of the poly(pyridine ether)s required strong acids such as methane or trifluoromethane sulfonic acid. The solubilities of the neutral and protonated polyethers derived from bisphenol A were studied in various solvents. The MALDI‐TOF mass spectra proved that protonation at 20–25 °C did not cause cleavage of ether bonds. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4781–4789, 2005     

Formation of linear and cyclic polyoxetanes in the cationic ring‐opening polymerization of 3‐allyloxymethyl‐3‐ethyloxetane and subsequent postpolymerization modification of poly(3‐allyloxymethyl‐3‐ethyloxetane)

The synthesis of 3‐allyloxymethyl‐3‐ethyloxetane (AllylEHO) and its polymerization with BF₃ × Et₂O is described in this study. Size exclusion chromatography (SEC) and membrane osmometry are used for the determination of molecular weights of the obtained products, ranging from M_n,SEC = 41,500‐131,500 g/mol. ¹H NMR spectroscopy, SEC, as well as MALDI‐TOF MS reveal the formation of cyclic tetramer beside low, but detectable concentrations of larger cyclic oligomers as by‐products during the polymerization process. These results help to understand mechanistically why attempts for a controlled homopolymerization of AllylEHO fail and why a controlled homopolymerization of oxetanes has not been described so far in the literature. Additionally, the high versatility of allyl‐functional polyoxetane for postpolymerization modification is proven by thiol–ene reactions with 3‐mercaptopropionic acid and N‐acetyl‐L ‐cysteine methyl ester. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Cyclic polypeptides by thermal polymerization of α‐amino acid N‐carboxyanhydrides

The NCAs of the following five amino acids were polymerized in bulk at 120 °C without addition of a catalyst or initiator: sarcosine (Sar), L ‐alanine (L ‐Ala), D ,L ‐phenylalanine (D ,L ‐Phe), D ,L ‐leucine (D ,L ‐Leu) and D ,L ‐valine (D,L ‐Val). The virgin reaction products were characterized by viscosity measurements ¹³C NMR spectroscopy and MALDI‐TOF mass spectrometry. In addition to numerous low molar mass byproducts cyclic polypeptides were formed as the main reaction products in the mass range above 800 Da. Two types of cyclic oligo‐ and polypeptides were detected in all cases with exception of sarcosine NCA, which only yielded one class of cyclic polypeptides. The efficient formation of cyclic oligo‐ and polypeptides explains why high molar mass polymers cannot be obtained by thermal polymerizations of α‐amino acid NCAs. Various polymerization mechanisms were discussed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4012–4020, 2008