Thermal and Mechanical Properties of Halogen‐Containing Aromatic Polyamides

Aromatic polyamides containing fluorine, chlorine, bromine and iodine have been prepared, and they have been evaluated by their mechanical and thermal properties. The method of polycondensation in solution at low temperature revealed as a very appropriate route to attain high molecular‐weight halogen‐containing polyisophthalamides (PIPA's) from aromatic diamines and 5‐halogenoisophthaloyl chlorides. High glass transition temperatures (T_g) were found for the set of polymers, in the range 250–350°C, showing a clear dependence on the size of the halogen incorporated, with values of T_g growing up in the series F < Cl < Br < I. On the other hand, thermal resistance was slightly impaired by the presence of halogens, as revealed by thermogravimetric analysis (TGA). In the same way, the mechanical strength was poorer than that of the parent unmodified PIPA's, by about 20%. All the polymers exhibited a mechanical relaxation at sub‐ambient temperature, about –70°C, associated to local molecular motions involving halogen atoms.     

Synthesis and characterization of aliphatic-aromatic poly(ether amide)s

Four aromatic diamines containing aliphatic spacers and Meta and para oriented oxyphenylene rings, and their corresponding hydrochlorides, were combined with isophthaloyl chloride (IPC) and terephthaloyl chloride (TPC) to give high molecular weight polyamides by interfacial and low-temperature solution methods. The synthesis and characterization of monomers and polymers are reported, and the differences observed in polycondensation yields, molecular weights and molecular weight distributions, as a function of the method of synthesis, are discussed. Values of number-average molecular weight (M?_n) up to 8 × 10⁴ g/mol and weight-average molecular weight (M?_w) up to 1 × 10⁵ g/mol could be measured by gel permeation chromatography using aromatic polyamide standards, and values of M?_n up to 2 × 10⁵ g/mol and M?_w up to 3.6 × 10⁵ g/mol by using polystyrene standards.     

Modifizierung von homo- und copolymeren des epichlorhydrins durch polymeranaloge umsetzungen

Poly(epichlorohydrin) and poly(epichlorohydrin-co-ethylene oxide) were modified by reaction with potassium thiocyanate (KSCN), tetrabutylammonium p-toluenesulfinate (NBu₄SO₂C₇H₇) and tetrabutylammonium benzenesulfinate (NBu₄SO₂C₆H₅). Though the substitution of chlorine in the polymers with these nucleophilic reagents in most cases is accompanied by side reactions, appropriate reaction conditions allow degrees of substitution higher than 90% to be obtained. The glass transition temperature (T_g) of the thiocyanate-modified homo- and copolymer exhibits only a small increase with increasing degree of substitution. While the T_g of the original homo- and copolymer is observed at ?20°C and ?38°C, respectively, the glass transition of the highly substituted homopolymer occurs at ?12°C and for the copolymer at ?31°C. On the other hand, the thiocyanate-modified polymers show a remarkably higher decomposition temperature of about 250°C as compared with that of the unmodified polymers (160–180°C). In addition, the solubility is markedly influenced by the substitution. While the original homo- and copolymers are soluble in, e.g., benzene and toluene, the highly modified products are only soluble in polar solvents such as THF, acetone, DMSO and diglyme. Introducing sulfonyl groups, the resulting polymers exhibit a glass transition temperature increased to a greater extent. For the homopolymer with the highest degree of substitution (98,3%), a T_g of 73°C is observed. Concerning the decomposition temperature, a drastical increase up to 370°C occurs. Finally the influence of phase transfer catalysts on the described reactions was investigated.     

Preparation of poly(amide-imide)s by direct polycondensation with triphenyl phosphite, 3. Poly(amide-imide)s based on bis(trimellitimide)s

Six dicarboxylic acids ( 1a–f ) were prepared from trimellitic anhydride and 4,4′-oxydianiline, 4,4′-methylenedianiline, 4,4′-sulfonyldianiline, benzidine, 1,6-hexamethylenediamine, and 4,4′-methylenedicyclohexylamine. These diacids were condensed directly with various aromatic diamines using triphenyl phosphite in 1-methyl-2-pyrrolidone/pyridine solution in the presence of calcium chloride. The inherent viscosity of the polymers is affected by the nature of the diamine and the solubility of the resulting polymers in the reaction media. The highest η_inh-value of a poly(amide-imide) obtained was 1,41 dl/g (in N,N-dimethylacetamide/5% LiCl at 30°C). Among the polymers, the wholly aromatic ones show better solubility, higher glass transition temperatures, and higher thermostability than the aliphatic-aromatic ones. Well-defined melting points (T_m) of most wholly aromatic poly(amide-imide)s were not obtained by differential scanning calorimetry (DSC); however, some poly(amide-imide)s containing aliphatic chains showed clear T_m in the first DSC heating traces. Measurements of wide-angle X-ray diffraction revealed that those polymers containing biphenyl or linear hexamethylene groups are partially crystalline. Flexible films with excellent tensile properties were cast from N,N-dimethylacetamide solutions of most of the wholly aromatic poly(amide-imide)s.     

Preparation of polyethers via proton acid catalyzed transetherification reactions

An approach for the preparation of polyethers by a transetherification route has been developed. This approach involves the melt condensation of a diol with a specifically designed diether in the presence of a catalyst to yield polyethers with the exclusion of two moles of a low boiling alcohol, in this case methanol. The diether monomers are designed so as to contain two labile benzyl methyl ether linkages that can readily undergo a transetherification process. These diether monomers ( 5 a and 5 b ) readily undergo transetherification polycondensation with di‐, tri‐ and tetraethylene glycols as well as with a variety of aliphatic diols to yield polymers of moderately high molecular weights. The glass transition temperatures (T_g) of the polymers decrease with increasing length of the diol. Melting transitions (T_m) are observed only in some polymers containing aliphatic units but those with the oligo(ethylene oxide) units are completely amorphous. Preliminary ionic conductivity studies indicate that the polyethers with oligo(ethylene oxide) units could serve as excellent candidates in solid polymer electrolyte applications.     

Synthesis and Properties of Novel Well‐Defined Alternating PPE/PPV Copolymers

The polycondensation reactions of luminophoric dialdehydes 5 and bisphosphonates 3 provide a new type of π‐conjugated polymers 7 with well‐defined structure (—Ar—C≡C—Ar—C≡C—Ar—CH=CH—Ar— CH=CH—)_n , which was confirmed by NMR, infrared and UV‐Vis spectroscopy. High molecular weight (M̄_w up to 500 000 g/mol), thermostable, soluble and transparent film‐forming materials were obtained. The grafting of large alkoxy side chains enhances the solubility and processability of the new compounds. The incorporation of triple bonds into the PPV backbone increases the oxidation and reduction potentials, thus making these polymers potentially good electron‐transporting materials if used in light‐emissive‐diode devices. The polymers are photoconductive and show very good photoluminescent properties in solution as well as in the solid state. Identical absorption (λ_max,abs = 445 nm) and emission (λ_max,em = 490 nm) behaviors were observed for all polymers in solution (CHCl₃), resulting in a fluorescence quantum yield of 70%, but the photophysical behavior in solid state was side group dependent. Polymer 7ac shows a very large Stokes shift (137 nm) and lower fluorescence quantum yield (19%), whereas 7aa , 7bb and 7ab , consisting of side groups equal to or longer than O(CH₂)₁₁CH₃ are characterized by smaller Stokes shifts (around 30 nm) and comparatively higher fluorescence quantum yields (34 to 44%).     

1H and 13C NMR spectra of poly(propyl α-bromoacrylate) and poly(methyl α-bromoacrylate)

The ¹³C NMR spectra measured at 25 MHz of the methyl and propyl esters of isotactic and syndiotactic poly(α-bromoacrylate) were sufficiently resolved to be analysed for pentad tacticity sequences. The pentad tacticity of the syndiotactic polymers prepared with free radical initiators at ?40°C agreed with those calculated for Bernoullian sequence distributions based on P_r values of 0,83–0,87. The tacticities of the isotactic polymers prepared with heterogeneous catalysts were determined on the basis of these assignments. Good internal consistency was obtained between the calculated and observed pentad proportions from the quaternary and carbonyl carbon peaks in the spectra of these polymers. The order of chemical shifts for the meso and racemic dyads and tetrads in these polymers were opposite to those found in the equivalent methacrylate polymers, but as with the latter, the ¹³C-T₁ values were longer in the isotactic than in the syndiotactic polymers.     

Saccharide polymers, 3. Synthesis and polymerization of a 5,6‐unsaturated fructofuranoid derivative

A new exo‐fructofuranoid monomer 5 was synthesized through a four‐step reaction. This unsaturated sugar monomer has been successfully tested in radical polymerization. Homo‐ and copolymerizations were carried out in solution under various conditions. The corresponding saccharide polymers were isolated as white powder and well characterized. Polymer compositions were determined by elemental analysis (C, H, N) and ¹H and ¹³C NMR. Polymerization parameters were determined for the binary system 1,2,3,4‐tetra‐O‐benzoyl‐6‐deoxy‐α‐D ‐threo‐5‐eno‐hexofuranose‐2‐uloside ( 5 )/MA giving the reactivity ratios r₁ = 0.47 for 5 and r₂ = 1.13 for MA. The thermal behaviour of saccharide polymers was investigated showing a linear relationship between the glass transition temperature (T_g) of the saccharide polymers and the sugar content. The saccharide polymers also showed optical activity and exhibit negative optical rotation. Both T_g and the specific optical rotations ([α]²⁰_D) increase with increasing sugar content.     

Synthesis of polyamide-sulfonamides by ring-opening polyaddition of N,N′-sebacoylbis(ethanesultam) with aliphatic diamines

The aminolysis of N-benzoylethanesultam ( 1 ) was conducted as a model compound study and was found to give almost exclusively ring-opened adduct. The ring-opening polyaddition of N,N′-sebacoylbis(ethanesultam) ( 5 ), synthesized from a sebacoyl chloride and ethanesultam ( 3 ), with aliphatic diamines in HMPT afforded a new class of polyamide-sulfonamides having inherent viscosities of 0,1–0,8dl.g^?1 in excellent yields. All of the polymers were soluble in polar aprotic solvents and some acidic solvents. These polymers began to decompose at around 300°C in air, as determined by TG.     

Polymerization of Butadiene with V(acac)3‐Methylaluminoxane Catalyst

Full Paper: Polymerization of butadiene (Bd) with V(acac)₃‐methylaluminoxane (MAO) catalyst was investigated. The microstructure of the polymer was found to depend strongly on the polymerization conditions. High polymerization temperature and high MAO/V(acac)₃ mole ratios were preferential to produce cis‐1,4 structure. Two kinds of active species were presumed from the GPC measurement of the polymers; one gives a high molecular weight polymer bearing high cis‐1,4 content, another affords a low molecular weight polymer with high trans‐1,4 content. A Solvent effect was observed. A polymer consisting of mainly trans‐1,4 unit was produced in CH₂Cl₂ in contrast to toluene and n‐heptane in which polymers consisting of mainly cis‐1,4 structure were observed. The addition of ethyl benzoate, triethylamine, chloranil, and tetracyanoquinodimethane to the V(acac)₃‐MAO catalyst gave an influence to not only the activity for the polymerization but also the microstructure of the polymer.     

Synthesis and characterization of poly(amide-imide)s containing 1,6-diamantane moieties in the main chain

A series of new poly(amide-imide)s were synthesized by direct polycondensation of the 1,6-bis(trimellitimido)diamantane ( 1 ) with various aromatic diamines in N-methyl-2-pyrrolidone (NMP) containing lithium chloride. The poly(amide-imide)s had inherent viscosities of 0.33–1.55 dL/g. The new polycyclic monomer 1 was synthesized from 1,6-diaminodiamantane with trimellitic anhydride. Dynamic mechanical analysis revealed polymers 3a – c to have main transitions at 385°C, 385°C, and 330°C, respectively. Moreover, these polymers were stable at high temperatures and maintained good mechanical properties (G′ ≈ 10⁸ Pa) up to temperatures close to the main transition well above 350°C. Their 5% weight loss temperatures ranged from 421 to 448°C in nitrogen, and from 417 to 426°C in air. A glass transition of poly(amide-imide)s 3 was not observed. Poly(amide-imide)s 3 (except 3e ) were soluble in NMP, pyridine, and o-chlorophenol. Some of the polymers ( 3a – c ) could be cast into flexible films. Their cast films had tensile strengths ranging from 35.5 to 46.9 MPa, elongations at break from 5.8 to 7.5%, and initial moduli from 1.8 to 2.1 GPa.     

Polymeric phthalocyanines and their precursors, 8. Synthesis and analytical characterization of polymers from 1,2,4,5-benzenetetracarbonitrile

Polymers 3 were prepared by reaction of 1,2,4,5-benzenetetracarbonitrile ( 2 ) or 2,3,9,10,16,17,23,24-(29H, 31H)-phthalocyanineoctacarbonitrile ( 5a ) with various metal salts or metals. The polymer structures were investigated by comparing their IR and UV/VIS spectra with those of 5 . Structurally uniform polymeric phthalocyanines 3 with a number of phthalocyanine units P_c ? 8, containing only nitrile end groups, were obtained from 2 or 5a with various copper salts. By saponification of 3 polymers (P_c ? 3) with carboxylic acid end groups were obtained. The reactions of 2 or 5a with other metal salts or metals yielded polymers of varying structural uniformity. Metal free 3a was also synthesized.     

Copolymerizations of l- and dl-menthyl vinyl ethers

Copolymerizations of l- and dl-menthyl vinyl ethers were carried out with BF₃O(C₂H₅)₂, Al(C₂H₅)₂Cl or SnCl₄ as catalyst. The yield and the mol. wt. of the polymers decreased as the d-monomer content in the feed monomer mixtures increased. The optical rotation changed linearly with the monomer composition, suggesting no preference of one of the monomers to the other did take place in the polymerization. The optical rotatory dispersions of all the polymers were expressed with DRUDE equation, and COTTON effect was not observed.     

Carbon-13 nuclear magnetic resonance studies of poly(N-vinylcarbazole)

The ¹³C NMR spectra of poly(N-vinylcarbazole), [poly(1-(N-carbazolyl)ethylene)], prepared under various polymerization conditions were measured at 25,03 MHz in 1,4-dioxane solution. The spectra were assigned by the chemical shifts and T₁ measurements of the polymers and N-ethylcarbazole as a model compound. The absorption of methylene and methine carbons varied by the polymerization methods. It was tentatively presumed that the polymers obtained by radical polymerization had syndiotactic-rich structures and the polymers prepared with BF₃O(C₂H₅)₂ isotactic-rich structures. The hindered internal rotation of the bulky carbazolyl group at the main chain of poly(N-vinylcarbazole) was also observed. The ¹³C NMR spectra indicated that the polymerization of N-vinylcarbazole with nitroethane proceeded by a radical mechanism while that with chloranil, (2,3,5,6-tetrachloro-1,4-benzoquinone), proceeded by a cationic mechanism.     

Stimuli‐Responsive Polymers Based on N‐Isopropylacrylamide and N‐Methacryloyl‐L‐Leucine

Linear and cross‐linked polymers capable of responding to both temperature and pH changes were synthesized by radical copolymerization of N‐isopropylacrylamide (NIPAAm) and N‐methacryloyl‐L ‐leucine (MALEU) in different NIPAAm/MALEU molar ratios. The solution behavior of linear polymers was investigated in 0.1 M NaCl and in citrate buffers pH 4.0, 4.5, 5.0 and 6.0. A sharp increase in the cloud point temperature (T_CP) was observed to occur around pH 4–5. Hydrogels were synthesized employing N,N ′‐methylenebisacrylamide as cross‐linking agent. The influence of composition and degree of cross‐linking on water absorption was investigated in 0.1 M NaCl and in citrate buffers pH 4.0 and 5.0. A reversible phase transition within a wide range of temperatures, depending on the composition and the pH, in accordance with the behavior of linear polymers, was observed.     

Poly(vinylsaccharide)s, 4. Synthesis and polymerization of 6-o-methylallylgalactose derivatives

Methylallyl ethers of 1,2:3,4-di-O-isopropylidene-D-galactopyranose and 1,2:3,4-di-O-cyclohexylidene-D-galactopyranose were synthesized as new monomers containing saccharide moieties and copolymerized with maleic anhydride. The hitherto unknown 6-O-(2-alkoxycarbonylallyl)-1,2:3,4-di-O-isopropylidene-D-galactopyranoses ( 8a and 8b; alkyl: methyl and ethyl, respectively) were prepared and polymerized under free radical conditions. The substances were characterized by ¹³C NMR, elemental analyses and molecular weight determinations. Water solubility of these polymers was obtained by removing the isopropylidene protecting groups. The inherent viscosities of these polymers, measured in 0,1 M Na₂SO₄ aqueous solution, were of the same order of magnitude as those of polyacrylamides of the corresponding degrees of polymerization.     

Synthesis and characterization of polymers containing 4-cyanobiphenyl-based side groups for nonlinear optical applications, 3. Poly(p-chloromethylstyrene) derivatives

Poly[p-(4′-cyanobiphenyl-4-yloxymethyl)styrene]s ( PCBMS ) were prepared by chemical modification of poly(p-chloromethylstyrene) with the sodium salt of 4-cyano-4′-hydroxybiphenyl or free radical polymerization of p-(4′-cyanobiphenyl-4-yloxymethyl)-styrene ( CBMS ). The latter method appeared to be a good one for the preparation of polymers with high glass transition temperature and high chromophore content if performed in dimethyl sulfoxide. There was no real evidence for liquid crystal properties in the resulting polymers, which resemble typical amorphous isotropic polymers. This indicates that these polymers should be considered to be polyethylene containing the benzyl ether of 4-cyano-4′-hydroxybiphenyl as the mesogenic group attached directly to the backbone, and not as polystyrenes containing the cyanobiphenyl group attached to the backbone through a ? O? CH₂? spacer. Some preliminary Corona poling experiments were performed, and the second harmonic generation coefficients d₃₁ and d₃₃, were measured by Maker fringe analysis. Interestingly, the ratio of d₃₃ to d₃₁ was found to be 6, which is much larger than the value of 3 predicted by the molecular statistical model for electric field poling of isotropic systems. This was attributed to conformational constraints on chromophore ordering as expected in such polymers containing no flexible spacer.     

Thermotropic Aromatic Poly(amide‐ether)s

Novel poly(amide ether)s were synthesized from aminophenyl‐terminated oxyethylene oligomers and terephthaloyl chloride or 4,4′‐biphenyldicarboxylic acid dichloride. The polymers were produced in high yield and high molecular weight (η_inh = 0.8–1.9 dl/g), and were characterized by elemental analyses, NMR spectroscopy and viscosity measurements. They showed low solubility in organic solvents, and a remarkable ability to develop high crystallinity, with melting temperatures in the range 300–370°C. Polymers containing biphenylene units formed stable mesophases (smectic) upon melting, as revealed by calorimetry, optical microscopy and X‐ray diffraction.     

Polymerization of tert-butyl methacrylate with Ni(acac)2-methylaluminoxane catalyst

The polymerization of tert-butyl methacrylate (tBMA) with nickel(II) acetylacetonate [Ni-(acac)₂] in combination with methylaluminoxane (MAO) was investigated. The binary catalyst is necessary to initiate the polymerization, however, high MAO/Ni mole ratios are not necessary to obtain high catalytic activity. A linear dependence of the molecular weight of the resulting polymers on polymer yield was observed, and the polydispersities of the polymers were relative narrow. The triad tacticity for the polymer obtained was determined to be mm = 3%, mr = 43%, rr = 54%.     

Synthesis of Double‐Hydrophilic Block Copolymers with Hydrophobic Moieties for the Controlled Crystallization of Minerals

A set of double hydrophilic block copolymers was synthesized on the basis of a branched poly(ethylene glycol)‐block‐poly(ethyleneimine) (PEG‐b‐PEI) block copolymer by polymer analogous reactions. Different hydrophobic moieties were successfully introduced as well as carboxylate, phosphonate, sulfonate and thiol groups leading to a library of only partially differing block copolymers. The analysis of the block copolymers by GPC turned out to be extremely difficult, as the multifunctional polymers tend to interact with various column materials. However, characterization of PEG‐b‐PEI was possible with ¹H NMR and analytical ultracentrifugation as well as with elemental analysis. These techniques revealed a significant amount of unbound PEG due to side reactions with PEI monomers or oligomers. The degree of the various functionalizations of PEG‐b‐PEI was determined by elemental analysis indicating that the sterically big phosphonic or sulfonic acid groups are only attached to the primary amino groups of the PEI block whereas the smaller thiol and carboxy groups can additionally be bound to secondary amino groups. The set of polymers was applied as additive in the crystallization of CaCO₃ yielding microparticles in all cases. Under the basic conditions of the experiment (pH > 8.5), both hydrophobically modified and unmodified polymers show almost the same influence on the CaCO₃ morphology, whereas the stabilization of the formed microparticles varies. However, the kind of functional group has a strong influence, with phosphonate and sulfonate as the substituents leading to the most significant changes in the CaCO₃ morphology.