Simulation of solid‐state polycondensation of nylon‐66

A new model of solid‐state polymerization of nylon‐6,6 has been developed. The polymer crystalline fraction is assumed to consist of only repeat units, leaving end‐groups and condensate in the amorphous fraction. Many effects neglected by previous models are considered, such as variable crystallinity, initial moisture and starting molecular weight. This model is compared to experimental data with good agreements. Differential scanning calorimetry graphs show that the crystalline structure phase tends to be increasingly perfect during heat treatment, indicative of the premelting temperature drawing near the melting point up to 14 °C after solid‐state polycondensation with little change of melting point. Copyright © 2000 John Wiley & Sons, Ltd.     

The effect of diamine length on the direct solid state polycondensation of semi‐aromatic nylon salts

In the current paper, a comparative study on the direct solid state polycondensation (DSSP) reaction of different terephthalate based semi‐aromatic salts (XT salts, X = 4–18) in the TGA micro‐reactor is reported. High purity XT salts were prepared in solution and were used as starting materials for DSSP. The reaction temperature (T_DSSP) for each salt was suitably selected as 20 °C–30 °C below the melting point T_m of the respective salt. The PAXT products were characterized by TGA/DSC, liquid ¹H‐NMR, and SEM. In the DSSP of XT salts, some diamine is always lost to the gas phase and as a consequence, the attainable molecular weight of the polymer formed gets limited by the unbalance of acid and amine end‐groups. The TGA curves show that as the diamine length increases and its volatility decreases, higher molecular weights are obtained. SEM pictures of the products reveal true solid character during the polymerization reaction up to and including PA10T, whereas PA5T, PA12T, and PA18T reveal stickiness and agglomeration during reaction. A possible mechanism explaining such behaviour is also provided. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2493–2506     

Synthesis and properties of new aromatic polysquaramide by solid‐state thermal polycondensation of salt monomer composed of squaric acid and bis(4‐aminophenyl) ether

The 1:1 stoichiometric salt monomer composed of squaric acid and bis(4‐aminophenyl) ether was successfully prepared and subjected to solid‐state thermal polycondensation under ordinary or high pressure, giving quite readily the aromatic polysquaramide with moderately high molecular weight. The polysquaramide formed was actually the random copolymer consisting of two component polymers, one of the main component being the polymer with a quasi‐aromatic mesoionic structure. The aromatic polysquaramide was crystalline and had a glass‐transition temperature of 245 °C, with an initial weight‐loss temperature of 400 °C in nitrogen. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2648–2655, 2002     

New polymer syntheses. CXI. Aliphatic polyesters by the ring‐opening polycondensation of glutaric anhydride with ethylene or trimethylene carbonate

Several polycondensations of ethylene carbonate with succinic anhydride or glutaric anhydride (GA) were conducted in bulk. Low molar mass polyesters were obtained with pyridine‐type catalysts and GA. Analogous polycondensations of trimethylene carbonate (TMC) and GA were successful when quinoline, 4‐(N,N‐dimethylamino)pyridine, or BF₃ · OEt₂ was used as a catalyst. Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectra revealed the formation of cyclic oligoesters and polyesters by backbiting degradation. Monomer mixtures containing an excess of TMC yielded copoly(ester carbonate)s with number‐average molecular weights up to 16,000 Da. Analogous copoly(ester carbonate)s were obtained from TMC and 3,3′‐tetramethylene glutaric anhydride. Furthermore, combined polycondensation/ring‐opening polymerization reactions of TMC and GA with L ‐lactide or ?‐caprolactone were studied. All copolymers were characterized by viscosity measurements and by IR, ¹H, and ¹³C NMR spectroscopy. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4357–4367, 2002     

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     

Control of chain ends of polyesters in polycondensation of AA and BB monomers by use of solid‐phase reagent

For selective synthesis of linear polyester having a functional group at one end, polycondensation between 1,4‐butanediol ( 1a ) and sebacoyl chloride ( 2a ) and between 1,12‐dodecanediol ( 1b ) and isophthaloyl chloride ( 2b ) was conducted in the presence of oxime resin or oxime silica gel, followed by cleavage of the formed polyester from the solid‐phase support with aniline. Matrix‐assisted laser desorption ionization time‐of‐flight mass spectra and ¹H NMR spectra of the cleaved polyester showed that the products contained not only polyester with anilide at one end ( poly 1 ), but also polyester with anilides at both ends ( poly 2 ). The product ratio of poly 1 to poly 2 ( poly 1 / poly 2 ) was dependent on monomers, monomer concentration, feed ratio of monomer to oxime moiety in the support, oxime content in the support, reaction solvent, and the nature of the support. Polyester with a high poly 1 / poly 2 ratio of 81/21 and moderate molecular weight (M_n = 1430 g/mol) was obtained by polycondensation of 1b and 2b in the presence of oxime silica gel in dichloromethane. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1379–1386     

Stereoblock poly(lactic acid): synthesis via solid-state polycondensation of a stereocomplexed mixture of poly(L-lactic acid) and poly(D-lactic acid)

Stereoblock poly(lactic acid) consisting of D- and L-lactate stereosequences can be successfully synthesized by solid-state polycondensation of a 1:1 mixture of poly(L-lactic acid) and poly(D-lactic acid). In the first step, melt-polycondensation of L- and D-lactic acids is conducted to synthesize poly(L-lactic acid) and poly(D-lactic acid) with a medium-molecular-weight, respectively. In the next step, these poly(L-lactic acid) and poly(D-lactic acid) are melt-blended in 1:1 ratio to allow formation of their stereocomplex. In the last step, this melt-blend is subjected to solid-state polycondensation at temperature where the dehydrative condensation is allowed to promote chain extension in the amorphous phase with the stereocomplex crystals preserved. Finally, stereoblock poly(lactic acid) having high-molecular-weight is obtained. The stereoblock poly(lactic acid) synthesized by this way shows a higher melting temperature in consequence of the controlled block lengths and the resulting higher-molecular-weight. The product characterization as well as the optimization of the polymerization conditions is described. Changes in M(w) of stereoblock poly(lactic acid) (sb-PLA) as a function of the reaction time.     

Substituent effects on the polycondensation of quinones with aromatic amines to form poly(quinone imine)s

The effect of alkyl groups on the polycondensation of aromatic diamines and quinones to form poly(quinone imine)s was investigated. Models were synthesized under standard conditions: 1 equiv of quinone was reacted with 2 equiv of aniline in the presence of titanium tetrachloride and 1,4‐diazabicyclo[2.2.2]octane. Only modest yields of diimines were obtained when alkyl substituents were introduced. Likewise, alkyl substituents were harmful in the polycondensation of both anthraquinones and benzoquinones with aromatic diamines. As for fluorine substituents, model reactions with either 1,5‐difluoroanthraquinone or 1,4‐difluoroanthraquinone with aniline proceeded in high yields. These model compounds for aromatic poly(quinone imine)s were characterized with ¹H NMR spectroscopy, ¹⁹F NMR spectroscopy, variable‐temperature ¹H NMR spectroscopy, and X‐ray crystal structure determination. Polymers of the difluoroanthraquinones with aromatic diamines were obtained in high yields, although not in high molecular weights, and no stereocontrol was found. Both p‐benzoquinones and anthraquinones were used as monomers in these polymerizations, and a fundamental difference in reactivity was observed. With the former, the polymerization behaved as a classical polycondensation and demanded exact reagent equivalence. With the anthraquinones, however, the polymerization proceeded by a condensation chain polymerization and was much more forgiving. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 43–54, 2002     

Non‐Stoichiometric Polycondensations and the Synthesis of High Molar Mass Polycondensates

This report presents a general overview of non‐stoichiometric step‐growth polymerizations (polycondensations). Three kinds of non‐stoichiometric polycondensations are defined and discussed for a₂ + b₂ monomer combinations. Depending on the kinetic scenario and on the experimental conditions, the excess of one monomer either strongly reduces or strongly enhances the average degree of polymerization (DP) relative to a stoichiometric polycondensation under identical conditions. As a result, telechelic oligomers or extremely high molar mass polymers (DPs > 1000) may be formed. Stoichiometric imbalance has in all cases the consequence that cyclization is largely suppressed in early stages of a polycondensation. Finally, non‐ stoichiometric “ a₂ + b_n ” polycondensations are discussed.     

Polycondensation of H3PO4 with glycerol: From branched structures to hydrolytically reversible gels

Direct polycondensation of glycerol (GL) and phosphoric acid (PA) has been studied for the first time. Reactions were performed at 100 °C–120 °C, and in spite of the formally A₃ + B₃ process soluble poly(glycerol phosphates) could be obtained up to the high conversions. This behavior stems from the side dealkylation reaction, that is, nucleophilic attack of the hydroxyl groups on the carbon atom in the already formed macromolecules, in place of the “normal” attack on the phosphorous atom. Besides, formation of cyclic structures frustrated both high polymers formation as well as early gelation. At certain, however, ratios of reactants and at the high enough conversions highly hygroscopic gels are formed. Acidic gels were swelling in water (over 1000%) and then were converted into relatively stable, soluble products, resulting from hydrolysis of the triester knots, and containing more hydrolytically stable diesters in the chains. Thus formed highly branched macromolecules could be converted back into a gel by condensation. This process could be repeated several times. The mechanism of polycondensation is proposed: like in the previously studied polycondensation of ethylene glycol with PA, formation of pyrophosphoric acid is preceding the actual polycondensation. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3533–3542     

Multidimensional solid‐state NMR studies of the structure and dynamics of pectic polysaccharides in uniformly 13C‐labeled Arabidopsis primary cell walls

Plant cell wall (CW) polysaccharides are responsible for the mechanical strength and growth of plant cells; however, the high‐resolution structure and dynamics of the CW polysaccharides are still poorly understood because of the insoluble nature of these molecules. Here, we use 2D and 3D magic‐angle‐spinning (MAS) solid‐state NMR (SSNMR) to investigate the structural role of pectins in the plant CW. Intact and partially depectinated primary CWs of Arabidopsis thaliana were uniformly labeled with ¹³C and their NMR spectra were compared. Recent ¹³C resonance assignment of the major polysaccharides in Arabidopsis thaliana CWs allowed us to determine the effects of depectination on the intermolecular packing and dynamics of the remaining wall polysaccharides. 2D and 3D correlation spectra show the suppression of pectin signals, confirming partial pectin removal by chelating agents and sodium carbonate. Importantly, higher cross peaks are observed in 2D and 3D ¹³C spectra of the depectinated CW, suggesting higher rigidity and denser packing of the remaining wall polysaccharides compared with the intact CW. ¹³C spin–lattice relaxation times and ¹H rotating‐frame spin–lattice relaxation times indicate that the polysaccharides are more rigid on both the nanosecond and microsecond timescales in the depectinated CW. Taken together, these results indicate that pectic polysaccharides are highly dynamic and endow the polysaccharide network of the primary CW with mobility and flexibility, which may be important for pectin functions. This study demonstrates the capability of multidimensional SSNMR to determine the intermolecular interactions and dynamic structures of complex plant materials under near‐native conditions. Copyright © 2012 John Wiley & Sons, Ltd.     

Perfluorocyclohexenyl aryl ether polymers via polycondensation of decafluorocyclohexene with bisphenols

A novel class of semifluorinated perfluorocyclohexenyl (PFCH) aryl ether homo/copolymers was successfully synthesized with high yield through the step‐growth polymerization of commercially available bisphenols and decafluorocyclohexene in the presence of a triethylamine base. The synthesized polymers exhibit variable thermal properties depending on the functional spacer group (R). PFCH aryl ether copolymers with random and alternating architectures were also prepared from versatile bis‐perfluorocyclohexenyl aryl ether monomers. The PFCH polymers show high thermal stabilities with a 5% decomposition temperature ranging from 359 to 444 °C in air and nitrogen atmosphere. These semifluorinated PFCH aromatic ether polymers contain intact enchained PFCH olefin moieties, making further reactions such as crosslinking and application specific functionalization possible. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 232–238     

Lipase-catalyzed polycondensation of dicarboxylic acid–divinyl esters and glycols to aliphatic polyesters

Lipase-catalyzed polymerization of dicarboxylic acid–divinyl esters with glycols has been performed. The vinyl esters used were divinyl adipate and divinyl sebacate. Lipases derived from Candida antarctica, Mucor miehei, Pseudomonas cepacia, and P. fluorescens showed high catalytic activity toward the present polymerization. Effects of solvent, reaction temperature, and enzyme amount were systematically investigated. A combination of divinyl adipate, 1,4-butanediol, and P. cepacia lipase afforded the highest molecular weight (2.1 × 10⁴). The yield of the polymer from divinyl sebacate was higher than that from divinyl adipate, whereas the opposite tendency was observed in the polymer molecular weight. Methylene chain length of α,ω-alkylene glycol also affected the polymerization behavior. The enzymatic polymerization of divinyl sebacate with cis-2-butene-1,4-diol and 2-butyne-1,4-diol resulted in the polymer containing unsaturated group in the polymer backbone. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2737–2745, 1999     

Synthesis of well-defined poly(p-benzamide) from chain-growth polycondensation and its application to block copolymers

Poly(p-benzamide) with a defined molecular weight and a low polydispersity and block copolymers containing this well-defined aramide was synthesized. Phenyl 4-(4-octyloxybenzylamino)benzoate ( 1b ) polymerized at room temperature in the presence of base and phenyl 4-nitrobenzoate ( 2a ) as an initiator in a chain-growth polycondensation manner to give well-defined aromatic polyamides having the 4-octyloxybenzyl groups as a protecting group on nitrogen in an amide. It was confirmed by a model reaction that deprotection of this protecting group proceeded completely with trifluoroacetic acid (TFA) without breaking the amide linkage. The utility of this approach to poly(p-benzamide) with a low polydispersity was demonstrated by the synthesis of block copolymers of poly(p-benzamide) and poly(N-octyl-p-benzamide) or poly(ethylene glycol). The SEM images of the supramolecular assemblies of the former block copolymer showed μm-sized bundles and aggregates of flake structures.     

Formation of higher cyclic oligomers in polyamide‐4,6

An example of morphology‐steered chemistry of cyclic oligomers with the example of polyamide‐4,6 (PA46) is discussed in this article. The cyclic oligoamide profiles of solid‐state post condensed PA46 show an unusual maximum for intermediate cycles consisting of 10 and 12 amide groups, which are formed in the initial stage of solid state post condensation. This is explained from the short chain length at the start of the post condensation, the preorganization of linear oligomers in the lamellar crystal structure, and the occurrence of amide units in the PA46 lamellar folds. Further the development of the cyclic oligomers up to the cyclic hexadecamide is followed on heating the base polymer in the melt at 310 °C, where it showed to react back to the theoretical Jacobsen and Stockmayer distribution. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Generation of radical species on polypropylene by alkylborane‐oxygen system and its application to graft polymerization

Graft polymerization of ethyl acrylate and n‐butyl acrylate onto surface of polypropylene (PP) beads (diameter: 3.2 mm) were carried out by using a redox system composed of triethylborane (Et₃B) and molecular oxygen in air. The amounts of the grafted polymers increased by prolonging a period of soaking PP beads in a solution of Et₃B in hexane, a less polar solvent of which affinity with PP would be higher than that of tetrahydrofuran, a highly polar solvent. These results implied that the present graft polymerization involved: (1) interpenetration of Et₃B into the surface area with the aid of hexane as a solvent, (2) its aerobic oxidation to generate a radical species, (3) abstraction of proton from PP by the radical species, and (4) initiation of polymerization from the resulting radical on the PP surface. Besides the acrylates, acrylic acid, and glycidyl methacrylate were also grafted onto the surface of PP to endow it with carboxyl and epoxy moieties, respectively. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6163–6167, 2009     

Synthesis of polyester having pendent hydroxyl groups via regioselective dehydration polycondensations of dicarboxylic acids and diols by low temperature polycondensation

In this article, we describe the one‐step synthesis of polyesters having pendent hydroxyl groups by Lewis acid‐catalyzed, regioselective, dehydration polycondensations of diols (glycerol and sorbitol) and dicarboxylic acids [tartaric acid (TA) and malic acid (MA)] containing pendent hydroxyl groups, using low temperature polycondensation technique. Direct polycondensations of TA or MA and 1,9‐nonanediol catalyzed by scandium trifluoromethanesulfonate [Sc(OTf)₃] successfully yielded linear polyesters having hydroxyl functionality (M_n = ca. 1.0 × 10⁴). To demonstrate the reactivity of the pendent hydroxyl group, a glycosidation was performed. Poly(nonamethylene L ‐malate) showed significant higher biodegradability, compared with poly(nonamethylene L ‐tartrate) or poly(nonamethylene succinate). Stable poly(nonamethylene L ‐tartrate) emulsion could be prepared using poly(vinyl alcohol) as the surfactant, although emulsions consisting of poly(nonamethylene succinate) were unstable and phase‐separated within a few days. Furthermore, direct polycondensations of TA and diethylene glycol (DEG) or triethylene glycol (TEG) successfully produced water‐soluble polyesters having hydroxyl groups. This new polycondensation system may be extremely effective not only for advanced material design using functional monomers but also for effective utilization of biomass resources as chemical substances. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5747–5759, 2009