Evaluation of triads in methyl methacrylate/methacrylic acid copolymers by 1H-NMR in different solvents and 13C-NMR

The probabilities of compositional-configurational triads in tactic and atactic methyl methacrylate/methacrylic acid copolymers are evaluated. After verification of the assignment of syndiotactic and isotactic triads in the ¹H-NMR spectra of tactic methyl methacrylate/methacrylic acid copolymers in three NMR solvents, the chemical shifts of the heterotactic triads are postulated by shift increments. The postulated assignment of the heterotactic triads is supported by comparison of the experimental ¹H-NMR peak intensities of atactic methyl methacrylate/pentadeuteromethacrylic acid copolymers and atactic pentadeuteromethyl methacrylate/methacrylic acid copolymers in three NMR solvents with calculated triad probabilities. The compositional and configurational parameters needed for the calculation of triad probabilities are determined. It is shown how the peak areas obtained from the two partially deuterated, atactic copolymers in different solvents may be combined to determine the probabilities of all compositional-configurational triads in atactic copolymers. Possibilities for the evaluation of triad probabilities from the ¹³C-NMR spectra of tactic and atactic methyl methacrylate/methacrylic acid copolymers are presented.     

Synthesis of novel polybutadiene-graft-poly(sodium methacrylate) amphiphilic copolymers as precursors for liquid crystalline graft copolymers

Well-defined polybutadiene-graft-poly(tert-butyl methacrylate) (PBD-g-PtBMA) copolymers were prepared by reaction of PtBMA chains end-capped with a tert-butyl 4-vinylbenzoate (tBVB) anion, with the selectively hydrosilylated 1,2-units of anionically synthesized PBD. Substitution of the tBVB anion for the anion of living PtBMA chains is required for the formation of the expected C-silylation product instead of the unstable O-silylation one. Subsequent hydrolysis of the poly(tert-butyl methacrylate) grafts followed by neutralization of the carboxylic acid groups by sodium hydroxide leads to amphiphilic polybutadiene-graft-poly(sodium methacrylate) (PBD-g-PNaMA) graft copolymers. These copolymers form unimeric micelles in water, as observed by dynamic light scattering (DLS). Non-covalent liquid crystalline graft copolymers were prepared by cation exchange between PBD-g-PNaMA copolymers and an ammonium containing smectic mesogen. These copolymers form a smectic mesophase which is microphase separated from PBD.     

Synthesis of water-soluble biologically active phenol (or catechol) containing copolymers of N-vinyl-2-pyrrolidone

Water-soluble N-vinyl-2-pyrrolidone (VP) copolymers containing phenol (or catechol) groups in the side chains were synthesized by reactions of copolymers of VP and crotonic acid (CA) with p-aminophenol and by reaction of p-nitrophenyl ester groups containing VP-CA copolymers with dopamine. It was established that phenol (or catechol) containing multiunit VP copolymers (which were characterized by GPC, viscometry, UV, IR and ¹H NMR spectroscopy) exhibit immunostimulating activity. In addition, the phenol-containing copolymers exhibit antitumor activity. The VP-CA-p-crotonoylaminophenol terpolymer can be used as a macromolecular carrier in the synthesis of a carcinogen-polymer antigen: a polymeric azo derivative of ß-naphthylamine.     

Electrochemical studies of some three component copolymers in nonaqueous media

Some three-component copolymers have been prepared by condensing formaldehyde with each of the following groups of monomeric species: (i) sulfanilic acid + p-toluidine + p-bromoaniline; (ii) p-aminobenzoic acid + p-toluidine + p-bromoaniline; (iii) sulfanilic acid p-aminobenzoic acid + p-bromoaniline. The composition of the copolymers has been deduced from electrometric titration studies in nonaqueous media, and Br content of the copolymers. Differentiation of acidic functional groups and the degree of polymerization of the copolymers could be obtained from their titration curves.     

Synthesis and Ozone Degradation of Alternating Copolymers of N‐Substituted Maleimides with Diene Monomers

Radical copolymerization of N‐substituted maleimides (RMIs) and maleic anhydride (MAn) in combination with 2,4‐dimethyl‐1,3‐pentadiene (DMPD) and 1,3‐pentadiene (PD) provides alternating copolymers with excellent thermal stability. Onset temperatures of decomposition are 280–331 and 336–371 °C for the copolymers with DMPD and PD, respectively. Glass transition temperatures of RMI copolymers are in a wide range of 54–138 °C depending on the bulkiness of N‐substituents. MAn copolymers are transformed to the corresponding RMI copolymers by postpolymerization reactions, which consist of quantitative addition of an alkylamine to an anhydride moiety of MAn copolymers and the subsequent heating. The copolymers synthesized in this study include ozone‐degradable carbon‐to‐carbon double bonds in their main chain. Molecular weight of the copolymers rapidly decreases by ozone degradation. Surface modification of casted polymer films is also performed by exposure to ozone‐containing air.     

Optically active copolymers of l-menthyl methacrylate and l-menthyl vinyl ether

Optically active copolymers of l-menthyl methacrylate or l-menthyl vinyl ether with maleic anhydride or N-(p-tolyl)maleimide were prepared. The optical activity of the co-polymers of l-menthyl methacrylate was almost proportional to the contents of l-menthyl methacrylate units in the copolymers, and after removal of the optically active side groups by hydrolysis, the optical activity disappeared. On the contrary, the optical activity of the copolymers of l-menthyl vinyl ether was considerably lower than the proportionality, and after removal of the side groups, optical activity opposite to the parent copolymers was observed. The cause for asymmetric induction was ascribed to the rigidity of the polymer chain.     

Well‐defined N‐Isopropylacrylamide Dual‐Sensitive Copolymers with LCST ≈38 °C in Different Architectures: Linear,Block and Star Polymers

Reversible addition‐fragmentation chain transfer (RAFT) polymerization is used to prepare temperature‐ and pH‐sensitive statistical copolymers with lower critical solution temperature (LCST) close to 38 °C at pH 7.4 based on N‐isopropylacrylamide and methacrylic acid derivative comonomers with a pK_a close to 6. Statistical copolymers are re‐activated to prepare amphiphilic block copolymers and star polymers with cross‐linked core. The LCST is maintained by varying the architecture; however, the LCST originated behaviour changes due to self‐aggregation. Statistical copolymers and short block copolymers show complex aggregation, whereas mid‐size block copolymers and star polymers show shrinkage of aggregate dimensions. The pH of the medium has a profound impact on the self‐assembling behaviour of the different polymer architectures.     

Copolymerisation von acetylen mit acetylenderivaten, 2. Copolymerisation von acetylen mit 3,3-dimethyl-1-butin

The coordinative copolymerization of acetylene with 3,3-dimethylbutyne in toluene with MoCl₅ was investigated. The copolymers were characterized spectroscopically as well as by means of gel permeation chromatography and differential scanning calorimetry. The copolymer composition was determined by means of the absorption coefficient of characteristic IR bands of 3,3-dimethyl-1-butin. Planar polyen sequences can be determined by means of UV spectroscopy. The transformation temperatures for the copolymers are below the temperature obtained for the cis-trans isomerization of pure polyacetylene. The molecular weight of the copolymers is lower than that of the copolymers of acetylene with phenylacetylene. The dependence of solubility and stability of the copolymers on the content of vinylene units shows the same tendency as observed for copolymers from acetylene and phenylacetylene; with increasing acetylene content the solubility decreases, while the instability increases. Increasing temperatures and light irradiation favour oxidation and degradation reactions. The oligomer fractions contain tert-butylbenzene, 1,3- and 1,4-di-tert-butylbenzene as well as 1,2,4,- and 1,3,5-tri-tert-butylbenzene.     

Biorecognition of sugar containing N-(2-hydroxypropyl)methacrylamide copolymers by immobilized lectin

The interactions of sugar containing N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers with Tetragonolobus purpureas (Lotus tetragonolobus) lectin immobilized on 4% beaded agarose have been studied. HPMA copolymers containing side-chains terminating in N-acylated amino sugars, namely, fucosylamine, galactosamine, glucosamine and mannosamine were synthesized and their biorecognition evaluated. As expected, only fucosylamine containing HPMA copolymers showed specific binding to the lectin. The dissociation constants (K_d) for HPMA copolymers were determined by frontal affinity chromatography. The binding constant was dependent on the amount of fucosylamine residues per macromolecule. An increase in fucosylamine content from 9,9 to 33,2 mol-% resulted in a decrease of K_d by one order of magnitude. Incorporation of hydrophobic side-chains such as glycylglycyl-5-[4-(2-aminoethylcarbamoyl)phenylazo]salicylic acid, 1′-(β-hydroxyethyl)-3′,3′-dimethyl-6-nitrospiro(2H-1-benzopyran-2,2′-indoline) (SP), or 1′-(β-glycylglycyloxyethyl)-3′,3′-dimethyl-6-nitrospiro(2H-1-benzopyran-2,2′-indoline) (GG-SP) into the copolymers increased the non-specific binding to the lectin. Photoinduced isomerization of bound spiropyrans to merocyanines was accompanied by changes in the conformation and biorecognition of HPMA copolymers. The results obtained demonstrated the impact of the structure and solution conformation of sugar containing HPMA copolymers on their biorecognition.     

Functional polymers and sequential copolymers by phase transfer catalysis, 1. Alternating block copolymers of unsaturated polyethers and aromatic poly(ether sulfone)s

Williamson etherification in the presence of phase transfer catalysts was successfully applied to the synthesis of alternating block copolymers and regular copolymers. Unsaturated polyethers( 5a and 5b ) containing chloroallylic (electrophilic) end groups (prepared from cis-or trans-1, 4-dichloro-2-butene and Bisphenol A) and aromatic poly(ether sulfone)s ( 3a ) containing terminal phenol (nucleophilic) groups were polycondensed in the presence of tetrabutylammonium hydrogen sulfate as phase transfer catalyst to give alternating block copolymers. The same telechelic polymers were chain-extended with dinucleophilic or dielectrophilic monomers under similar reaction conditions. Both the regular copolymers and the alternating block copolymers were characterized by gel pormeation chromatography and DSC.     

Block copolymers by radical polymerization 3. Block copolymers of styrene,methyl acrylate,n-methyl-n-vinylacetamide, 1-vinyl-2-pyrrolidone

A polyazoinitiator obtained from 2,2′-azoisobutyronitrile (AIBN) and a diol is used to prepare block copolymers according to the Smets procedure. Partial decomposition of the polyazoinitiator in presence of a monomer results in an azogroup-containing prepolymer. Block copolymers are obtained decomposing the remaining azo groups in presence of a second monomer. Examples investigated are styrene/methyl acrylate, styrene/N-methyl-N-vinylacetamide, methyl acrylate/N-methyl-N-vinylacetamide, 1-vinyl-2-pyrrolidone/acrylonitrile. Homopolymers are produced simultaneously. Up to 70% of block copolymers are formed in these reactions. Block copolymers of styrene/methyl acrylate have hard/soft segmented molecules. It is an elastic material with spherical, cylindrical and lamellar, resp. domain structures, depending on the composition.     

Copolymerisation von acetylen mit acetylenderivaten, 1. Copolymerisation von acetylen mit phenylacetylen

Copolymers were obtained from acetylene and phenylacetylene by coordinative polymerization with MoCl₅ as a catalyst in toluene as solvent. The copolymers were characterized by spectroscopic methods as well as by means of differential scanning calorimetry and gel permeation chromatography. The fraction of phenylvinylene units in the copolymers was determined by means of UV spectroscopy as well as the conjugation length of planar double bonds which increases with increasing fraction of vinylene units. The fraction of vinylene units in the copolymers was determined by IR spectroscopy. DSC measurements indicate the transformation temperature for isomerization, cyclization, aromatization and chain scission to decrease with increasing fraction of vinylene units. At high contents of vinylene units in the copolymers a trans-cisoide configuration is realised, while for pure polyphenylacetylene and copolymers with a low vinylene fraction the cis-transoide configuration is favoured. With increasing content of vinylene units the solubility of the copolymers decreases, while oxidizability and degradation reactions increase. These reactions are favoured at higher temperatures and upon light irradiation. The oligomeric fractions of the copolymers indicate the presence of biphenyl o,- m- and p-terphenyl, 1,1′:2′,1″:4′,1 ?- and 1,1′:3′,1″:5′,1 ?-quaterphenyl.     

Caractérisation de réactions primaires de dégradation oxydante au cours de l'autoxydation des polyoxyéthylènes à 25°C: Étude en solution aqueuse avee amorçage par radiolyse du solvant. II. Arguments pour un mécanisme monomoléculaire de décomposition des radicaux peroxyles

Cationic copolymerizations of furfural were carried out with several vinyl monomers. No copolymers were obtained with some hydrocarbon comonomers. At low temperatures furfural copolymerized with vinyl ethers selectively through the aldehyde group. On the other hand, deeply-colored copolymers of complex structures were formed at higher temperatures (ca. 0°C). Three typical vinyl ethers (p-tolyl vinyl ether, dihydropyran, and divinyl ether) were selected as comonomers, and their copolymerization behaviour studied in detail. The monomer reactivity ratios for furfural (M₁) and p-tolyl vinyl ether (M₂) were r₁ = 0,15 ± 0,15, r₂ = 0,25 ± 0,05. The furfural (FF) contents were fairly independent of the monomer feeds when dihydropyran (DHP) and divinyl ether (DVE) were used as comonomers: 37–47% for FF-DHP copolymers and 40–50% for FF-DVE copolymers. More than half of the second vinyl groups were consumed in the FF-DVE copolymers indicating the formation of 1,3-dioxane rings as in the case of benzaldehyde-DVE copolymers.     

Synthesis of ABC-triblock copolymers for light emitting diodes

In this paper we report on the synthesis and characterization of ABC-triblock copolymers poly(N-vinylcarbazole)-block-poly(4-(1-pyrenyl)butyl vinyl ether)-block-poly(2-[4-(2-phenyl-1,3,4-oxdiazolyl)phenyloxy]ethyl vinyl ether) 15 . The ABC-triblock copolymers were synthesized by sequential living cationic polymerization of N-vinylcarbazole 11 , 4-(1-pyrenyl)butyl vinyl ether 10 and 2-chloroethyl vinyl ether 3 . In a second step, the reactive pendant chloro groups of the poly(2-chloroethyl vinyl ether) segment of the block copolymers were substituted with 2-(4-hydroxyphenyl)-5-phenyl-1,3,4-oxadiazole 6 to form fully functionalized ABC'-triblock copolymers. The molecular weight of the block copolymers varied from M _n = 4800 to 14000. The thermal behavior is discussed with respect to the block copolymer composition and compared with corresponding polymer blends. LED characteristics of a single layer device for one of the block copolymers are presented as an example.     

Sodium Poly(α,L‐glutamate)/Ethylene Oxide‐Propylene Oxide (Block and Random) Copolymer Macromolecular Complexes. Method of Preparation and Structure of Complex

Macromolecular complexes of sodium poly(α,L ‐glutamate) (PGNA) (molecular weight (MW) 1, 49 and 71 k) and ethylene oxide‐propylene oxide tri‐block copolymer (MW 8 400) have been prepared by a novel method involving dehydration of reverse micelles (DRM method). This series of complexes was compared with the complexes of PGNA (MW 1, 49 and 71 k)/ethylene oxide‐propylene oxide random and tri‐block copolymers prepared by the common method involving evaporation of aqueous mixtures (EAM method). By the DRM process fifteen times more copolymer was incorporated in the pure macromolecular complex than by the EAM process. CD spectra of the EAM series of complexes showed formation of α‐helical PGNA conformation as evidenced by the observation of +ve peak at 194 nm and two –ve peaks at 201 and 221 nm. Formation of the α‐helical conformation is further supported by FT‐IR spectroscopy. On the other hand, CD spectra of the DRM macromolecular complexes showed neither α‐helical nor random conformation, and the spectra may be attributed to a distorted helical PGNA conformation. DSC studies revealed that the copolymers in EAM macromolecular complexes were intimately blended with PGNA, while in the DRM series only 65% of the copolymer were blended at the molecular level, with the rest present as a pure copolymer domain. ²³Na NMR spectra of both series of complexes showed presence of free sodium ions indicative of dissociated Na⁺—O dipolar interactions in aqueous solution. Hydrophobic interaction between PGNA and copolymer remained intact even in very dilute solutions of both series of complexes as observed by strong 2D‐NOESY ¹H NMR correlation between β and γ CH₂ groups of PGNA and CH₂ groups of copolymers. However, in the DRM series, only the CH₂ groups of PEO blocks of the PEO‐PPO‐PEO copolymer showed the 2D‐NOESY ¹H NMR correlation indicating that only the PEO blocks are involved in the complex formation. The PPO block that had no interaction with PGNA may have formed pure PPO domains. NMR data combined with the DSC, CD and FT‐IR data suggest that the structure of both series of macromolecular complex is a composite composed of copolymer molecules intimately interacting with PGNA chains. Interactions between β and γ groups of PGNA side groups with CH₂ groups of the copolymer are involved in forming the complex. 2D‐NOESY ¹H NMR correlation further indicate that both the DRM and EAM series of macromolecular complexes are stable in water for at least seven weeks.     

Stress‐Strain Behaviour,Microhardness, and Dynamic Mechanical Properties of a Series of Ethylene‐Norbornene Copolymers

Ten copolymers of ethylene and norbornene, synthesised by a metallocene catalyst, covering the composition range from 31 to 62 mol‐% of norbornene, have been studied by stress‐strain, microhardness and dynamic mechanical measurements. These copolymers show a single glass transition and the correlation between T_g and the norbornene content is quite good. The inclusion in the polymer chain of rigid norbornene units, with the corresponding increase in T_g, leads to considerably higher Young moduli and microhardness values in these cycloolefin copolymers. The same result is found for the yield stress: this parameter shows an increase by a factor of two in the studied copolymers. Two relaxations, α and γ have been found by means of dynamic mechanical analysis of these copolymers. The results show that the γ relaxation has a similar origin to that of polyethylene and therefore its intensity diminishes as the proportion of ethylene segments in the copolymers decreases. On the contrary, the α relaxation of the copolymers has a completely different origin than that of polyethylene. Thus, this relaxation represents the glass transition in the copolymers, associated with the amorphous character, while it is attributed to motions in the crystalline regions of the parent homopolymer, polyethylene.     

Morphology of (methoxyethoxy/trifluoroethoxy)phosphazene copolymers

Block copolymers were synthesized by the anionically initiated copolymerization of (CH₃OCH₂CH₂O)(CF₃CH₂O)₂P? NSi(CH₃)₃, followed by the addition of (CF₃CH₂O)₃P? NSi(CH₃)₃. Random copolymers were made by simultaneous polymerization of these monomers. These copolymers exhibit a linear dependency on the mole fraction “m” of the repeating units bearing a methoxyethoxy pendant side group as well as on molecular weights. The thermal and morphological characteristics of the block copolymers are different from those of the random copolymers of analogous “m” and molecular weight. All copolymers undergo a mesophase T(1) transition for a range of temperatures depending upon “m” and molecular weights of the copolymers. Morphological and structural features essentially resemble those of the low molecular weight (trifluoroethoxy)phosphazene homopolymer. Upon heating and cooling the solution cast copolymer specimens through T(1), most of them transform into an orthorhombic form with the unit cell dimensions a = 2,060 nm, b = 0,940 nm and c = 0,486 nm from their initial monoclinic form with a = 1,003 nm, b = 0,937 nm, c = 0,486 nm and γ γ 91°. These unit cell dimensions agree completely with those of the low molecular weight PBFP. Complicated morphologies comprised of square and globular shapes that depend upon the copolymer composition were obtained from dilute tetrahydrofuran/p-xylene copolymer solutions. Electron microscopy directly reveals that chain extension occurs for the meltcrystallized copolymer specimen. The non-crystallizable minor component in the block copolymers is rejected from the crystal lattice. In the random copolymers, the methoxyethoxy pendant side group enters into the crystal lattice and influences their morphological and structural features.     

Study of the water structure in poly(methyl methacrylate-block-2-hydroxyethyl methacrylate) and its relationship to platelet adhesion on the copolymer surface

The water structure and platelet compatibility of poly(methyl methacrylate (MMA)-block-2-hydroxyethyl methacrylate (HEMA)) were investigated. The molecular weight (Mn) of the polyHEMA segment was kept constant (average: 9600), while the Mn of the polyMMA segment was varied from 1340 to 7390. The equilibrium water content of the copolymers was found to be mainly governed by the HEMA content. The water structure in the copolymers was characterized in terms of the amounts of non-freezing and freezing water (abbreviated as W_nf and W_fz, respectively) using differential scanning calorimetry. It was found that the W_nf for the copolymers were higher than those estimated from the W_nf for the HEMA and MMA homopolymers and that the amount of excess non-freezing water depended on the polyMMA segment length. In addition, X-ray diffraction analysis revealed that some of the copolymers had cold-crystallizable water. These facts suggested that the polyMMA segments were involved in determining the water structures in the copolymers. Furthermore, the platelet compatibility of the copolymers was improved as compared to that of the HEMA homopolymer. It was therefore concluded that the platelet compatibility of the copolymer was related to the amount of excess non-freezing water.     

Effect of poly(dimethylsiloxane)-block-poly(oligo (ethylene glycol) methacrylate) amphiphilic block copolymers on dermal fibroblast viability and proliferation

Abstract

In this work, well-defined poly(dimethylsiloxane)-b-poly(oligo (ethylene glycol) methacrylate) (PDMS-b-POEGMA) amphiphilic block copolymers were synthesized and their effect on human dermal fibroblast were investigated. Anionic ring opening polymerization (ROP) and atom transfer radical polymerization (ATRP) were used to synthesis the block copolymers. The molecular weight of synthesized copolymers ranged from 1000 to 2300?Da by changing the number of both PDMS and POEGMA units. It was found that the copolymer having low molecular weight decreased the fibroblast viability and proliferation by inducing apoptosis. It was proved by flow cytometry and TUNEL assay that human dermal fibroblast experienced apoptosis after exposure to synthesized amphiphilic copolymers. The results of this work suggest the use of PDMS-b-POEGMA amphiphilic copolymers with low molecular weight for hypertrophic scars remediation.     

Polymers from multifunctional isocyanates, 13. Functional polymers from N-substituted poly(maleimide-alt-isopropenyl isocyanate)s

Alternating copolymers from isopropenyl isocyanate and N-substituted maleimides (N-phenyl, N-tetradecyl- and N-octadecylmaleimide) were synthesized for the first time. The reactive copolymers with regular structure have an isocyanate group in the constitutional repeating unit which allows modification and functionalization in a polymer analogous reaction. Functionalization has been demonstrated with examples of amphiphilic copolymers having the hydrophobic and the hydrophilic chain attached to the polymer backbone in a regular alternating fashion. A second example is an alternating copolymer with an NLO-chromophore attached to the polymer.