A method for determining sequence distributions in ethylene-1-butene copolymers by 13C NMR

Sequence distributions of the 1-butene comonomers in ethylene-1-butene copolymers were determined by analyzing the ¹³C NMR spectra using an optimization calculation technique. The proposed method takes the possible errors in NMR measurements into account. Applying the method to the spectra of some linear low density polyethylenes with 1-butene as the comonomer gave physically reasonable values of triad comonomer distribution. The method was thought to be useful by giving the possible maximum and minimum triad concentrations reflecting the chain structures. We also tried to use the method for determination of larger sequence structures over triad distribution. Received: 10 February 1997/Revised: 31 March 1997/Accepted: 2 April 1997     

Reaction of poly(vinyl alcohol) with diketene

A study has been made on the modification of poly (vinyl alcohol) with diketene using tertiary amines as catalysts. The structure of the resulting polymers was determined by means of IR, ¹H- and ¹³C-NMR spectroscopy as well as by chemical analysis. Vinyl alcohol-vinyl acetoacetate (VAL-VAA) copolymers were obtained. It has been found a linear dependence of reaction rate on polymer, diketene and pyridine concentrations, respectively. The activation energy was found to be 35.5 kJ/mol (8.5 kcal/mol). ¹³C-NMR spectroscopy was used for the determination of the sequence distribution in VAL-VAA copolymers. The obtained results show that VAA units have a little alternating tendency in the copolymer chain. Polymeric chelates between VAL-VAA copolymers and cupric ions have been prepared. It is noteworthy that not all the β-keto ester groups in the VAL-VAA copolymers participate in binding cupric ions.     

Morphological and kinetic partitioning of comonomer in random propylene 1-butene copolymers

The partitioning of the 1-butene co-unit between crystalline and non-crystalline regions of random, homogeneous propylene 1-butene copolymers (PB) has been studied by WAXD, ¹³C NMR, and FTIR in a series of copolymers with a concentration of 1-butene ranging from 2 to ～ 20 mol%. A partial inclusion of the 1-butene co-unit in the crystallites is identified by the expansion of the unit cell, and quantified by extracting ¹³C NMR spectra of the crystalline regions. For slowly cooled copolymers, about 30% of the chain’s 1-butene co-units are incorporated into the crystallites. Analyses of FTIR absorbances associated with crystalline 1-butene provide additional quantitative information on the morphological partitioning of the co-unit and give evidence to support that the incorporation of the comonomer into the crystalline regions is controlled by crystallization kinetics. The presence of the comonomer in the crystalline region affects the observed vibration of the most sensitive iPP 3/1 regularity bands associated with the evolution of crystallites, i.e. 841 cm^?1 (12 isotactic units). The frequency of this band shifts toward higher values with increasing comonomer and with increasing undercooling, in support of an increasing concentration of entrapped crystalline 1-butene. The frequency shift is absent in copolymers with co-units that are excluded from the crystalline regions, such as the 1-octene comonomer.     

Charge transfer copolymerization and properties of isopropyl methacrylate with acrylonitrile and methacrylonitrile

Isopropyl methacrylate (IPMA) with Acrylonitrile (AN) and Methacrylonitrile (MAN) copolymers of different copositions were prepared at 60°C and 80°C, respectively, using a mixture of n-Butylamine (nBA) and carbon tetrachloride (CCl₄) in dimethyl sulphoxide (DMSO) as a charge transfer (CT) initiator. The percentage composition of the copolymers was established by elemental analysis. The copolymerization reactivity ratios were computed by the Kelen–Tudos method. In both the systems, IPMA was found to be more reactive; the copolymers sequence was random in nature. The copolymers were characterized by IR, ¹H-NMR, ¹³C-NMR spectroscopy and intrinsic viscosity measurements in dimethyl formamide (DMF) at 30±0.1°C. The thermal behavior of the AN-IPMA copolymers was studied by thermogravimetry (TG) in air. The thermal stability increased, with increasing AN content in the copolymer chain. The solubility parameter of AN-IPMA copolymer was evaluated by studying the intrinsic viscosity in different solvents. The solubility parameter of the copolymer was found to be 9.7 (cal/cc)^1/2.     

Novel copolymers of styrene. 1. Alkyl ring-substituted 2-cyano-3-phenyl 2-propenamides

Novel electrophilic trisubstituted ethylene monomers, alkyl ring-substituted 2-cyano-3-phenyl-2-propenamides, RC₆H₄CH=C(CN)CONH₂ (where R is 2-methyl, 3-methyl, 4-methyl, 4-ethyl, 4-i-propyl, 4-i-butyl, and 4-t-butyl), were synthesized by potassium hydroxide catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and cyanoacetamide, and characterized by CHN elemental analysis, IR, ¹H- and ¹³C-NMR. Novel copolymers of the ethylenes and styrene were prepared at equimolar monomer feed composition by solution copolymerization in the presence of a radical initiator, AIBN at 70 °C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, ¹H- and ¹³C-NMR, GPC, DSC, and TGA. High T _g of the copolymers in comparison with that of polystyrene indicates a substantial decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 200–500 °C range with residue (5–7 wt%), which then decomposed in the 500–800 °C range.     

Sulfur containing polymers

Summary Copolymers containing -S-CO-S-and/or -O-CO-S-groups have been synthesized mainly by interfacial polycondensation.Different chemical structures were obtained by reacting 1,3-benzene dithiol (BDT) respectively with phosgene alone, phosgene and bisphenol-A (BPA), bischloroformate of BPA, BPA polycarbonate oligomers and by reacting phosgene with the products of BPA polycarbonate degraded with BDT. The chemical structures of the copolymers were investigated by IR, ¹H-NMR and ¹³C-NMR; molecular weights were determined by viscometry and vapor pressure osmometry. Although no attempt was made to find the optimum conditions for high molecular weight, some copolymers with fairly high mol. weight were obtained.     

Poly(vinyl alcohol) modification with n-alkyl chloroformates

This work deals with the modification reaction of poly(vinyl alcohol) with n-alkyl chloroformates using pyridine as catalyst. The structure of the modified polymers was determined by means of IR, ¹H and ¹³C-NMR spectroscopy as well as by chemical analysis. Vinyl alcohol-vinyl n-alkyl carbonate copolymers were obtained. The presence of cyclic carbonates has not been observed. It has been found a linear dependence of reaction rate on polymer, n-alkyl chloroformates, and pyridine concentrations, respectively. The activation energy found was of 15.4 kcal/mol. The water absorbed in the copolymers made it reasonable to conclude that the hydrophilic character of the copolymers decreased progressively when either the carbonate groups content or the side chain length increased. Water insoluble alcohol-vinyl n-alkyl carbonate copolymers were hydrolyzed in an alkaline medium. They were found to recover their solubility in water after a certain hydrolysis extent was reached.     

Spontaneous copolymerization of 2-phenyl-2-oxazoline with cyclic carboxylic anhydrides

Summary The copolymers obtained by the spontaneous reaction between 2-phenyl-2-oxazoline (PhOx) and different anhydrides (succinic-SA, maleic-MA and phthalic-PA) in the absence of an added initiator have been studied. The copolymers were characterized by FTIR and ¹³C-NMR spectroscopies. Compositions were determined by quantitative elemental analysis and average molecular weights were obtained by GPC. The PhOx/MA and PhOx/PA were found to be alternating copolymers, whereas the PhOx/SA copolymer was a statistical one, rich in PhOx.     

Glycidyl methacrylate and N-vinyl-2-pyrrolidone copolymers: Synthesis,characterization, and reactivity ratios

Free radical copolymerization of glycidyl methacrylate (GMA) and N-vinyl-2-pyrrolidone (VPD) was carried out using 2,2′-azobisisobutyronitrile (AIBN), in chloroform at 60°C. The polymers were characterized by IR and ¹³C-NMR spectroscopic methods. The percentage composition of the copolymers were established by microelemental analysis and by ¹³C-NMR spectroscopy. The copolymerization reactivity ratios were computed using the Fineman-Ross method, the Kelen-Tudos method, and the extended Kelen-Tudos method. The molecular weights of the copolymers were obtained by GPC measurements. Thermal properties of the homo- and copolymers were also studied by thermogravimetric analysis. The copolymers were tested as adhesives for leather-to-leather and leather-torubber bonding.     

Formation and reorganization of the mesophase of random copolymers of propylene and 1-butene

Fast scanning chip calorimetry (FSC) has been employed to study the kinetics of formation of the mesophase of random copolymers of propylene and 1-butene from the glassy amorphous state and its reorganization on heating. The experiments performed consistently prove a distinct decrease of the rate of mesophase formation with increasing concentration of 1-butene chain defects. The time required for isothermal mesophase formation at 300 K is of the order of 0.1 s in case of the homopolymer, while it is prolonged by one order of magnitude to 1 s in the copolymer with 11 mol-% 1-butene. Similar, cold-ordering of amorphous structure on continuous heating at 1000 K s⁻¹ is only completed in the homopolymer while it is almost completely suppressed in the random copolymer containing about 11 mol-% 1-butene. The perfection of the mesophase and/or its reorganization into crystals is faster in the homopolymer than in copolymers containing 1-butene. The critical heating rate for complete inhibition of perfection and reorganization is reduced from about 40,000 K s⁻¹ in the homopolymer to about 10,000 K s⁻¹ in copolymers. The reduced rate of mesophase formation in random copolymers of propylene and 1-butene is attributed to the decrease of the thermodynamic driving force for the phase transformation.     

Copolymers of Phenoxyethyl Methacrylate with Butyl Methacrylate: Synthesis,Characterization and Reactivity Ratios

Phenoxyethyl methacrylate (POEMA) and butyl methacrylate (BMA) were copolymerized by free-radical copolymerization using α,α′-azobisisobutyronitrile (AIBN) in 2-butanone solution at 333±1 K. Copolymers were characterized by FTIR, ¹H-NMR and ¹³C-NMR spectroscopic methods and by comparison of the spectra with the corresponding homopolymers. Thermogravimetric analysis of the copolymers was carried out in order to know their thermal stability. Copolymer composition was established by ¹H-NMR analysis. Monomer reactivity ratios (MRR) were computed using the classical Fineman – Ross (FR) and Kelen – Tüdos (KT) procedures. MRR were also estimated using a nonlinear computational fitting procedure, known as reactivity ratios error in variable model (RREVM). The mean sequence lengths of the copolymers were estimated and suggest that random copolymers were obtained.     

Influence of primary structure on thermal oxidative degradation of polypropylene impact copolymer

Summary Thermal oxidative degradation was carried out using four kinds of polypropylene impact copolymers, and the relationship between primary structure and degradation behavior was investigated by the results of ¹³C-NMR, TEM, GPC and the determination of hydroperoxide value (HPO) and number of chain scission (NCS). The degradation behavior mainly depended on the ethylene content and on the tacticity. The thermal degradation was found to be controllable by the primary structure.     

A study on cytocompatible poly(chitosan-g-l-lactic acid)

A novel cytocompatible graft copolymer of chitosan and l-lactic acid (CL) was prepared by grafting l-lactic acid onto the amino groups in chitosan without a catalyst. The structures of the CL graft copolymers were characterized by FTIR, ¹³C-NMR and X-ray measurements. Degree of substitution and side-chain length were evaluated from salicylaldehyde and elemental analysis. The tensile strength and water uptake of the CL copolymers films were investigated as a function of feed ratio of LA/CS. The influence of pH on the swelling behavior of the copolymer films was determined and interpreted. Fibroblast culture was performed to evaluate cell proliferation on the copolymers films. The results showed that the cell growth rate on the copolymers films is faster than chitosan obviously.     

Poly[N-(hydroxyethyl)ethyleneimine-co-phenyl succinic anhydride] Synthesis and structure

Summary Five copolymers from N-(hydroxyethyl)ethyleneimine as nucleophilic monomer and phenylsuccinic anhydride (PhSAn) as electrophilic monomer, were synthesized according to the spontaneous copolymerization concept. These copolymers were characterized by elemental analysis, FT-IR, ¹H-NMR, and ¹³C-NMR spectroscopy. The copolymer composition determined from the ¹H-NMR spectra showed that the copolymers are not alternating. According to all the data, it was suggested a copolymer structure which includes ester and anhydride bonds. The molecular weights determined by vapor pressure osmometry ranged between 5.100 and 6.100 g/mol. Received: 12 February 1999/Revised version: 5 October 1999/Accepted: 5 October 1999     

Homogeneous and heterogeneous copolymerization of styrene and sulfur dioxide using the (CH3)3COOH/SO2 redox system

Styrene was copolymerized with sulfur dioxide in the presence of tert-butyl hydroperoxide under homogeneous and heterogeneous conditions. The rate of copolymer formation decreases in the order emulsion, suspension, organic–aqueous, and organic solution. The rate also depends on reaction time, temperature, solvent, and initiator concentration. Several physical methods used to characterize these copolymers, including IR, ¹³C-NMR, elemental analysis, viscosity, softening point, and isothermal aging. Analysis of the composition of the resulting copolymers revealed that there are on the average about two molecules of styrene per SO₂ present on the copolymer chain. ¹³C-NMR suggests that these copolymers are made up mostly of the MSM, SMM, and MMS triad monomer sequences whereas the SMS and MMM are present in small amounts. Characterization of polystyrene homopolymers shows that there is lack of stereoregularity in both homogeneous and heterogeneous polymerization systems.     

Synthesis and solubility of polylactide-co-poly(amino acid) random copolymer

Random copolymers of polylactide-co-poly(amino acids) with a molecule weight range of 5,000–20,000 g/mol were obtained by ring-opening polymerization of l-lactic acid O-carboxyanhydride with amino acid-N-carboxyl anhydride in the presence of DMAP as an initiator. The structures of the copolymers were characterized with IR, ¹H-NMR, ¹³C-NMR, and GPC. The results show that the polymerization activity of amino acid-N-carboxyl anhydride is higher than that of l-lactic acid O-carboxyanhydride. Copolymers of polylactide-co-poly(amino acid) can improve the solubility of poly(amino acid) in organic solvents.     

Microstructure of Ethylene/Propylene Random Copolymers Prepared by a Fluorinated Bis(phenoxy-imine)Ti Catalyst

Summary Living copolymerization of ethylene and propylene was catalyzed by a fluorine-containing bis(phenoxy-imine) titanium catalyst. A series of ethylene-propylene copolymers with different propylene contents were prepared and the copolymers were characterized by ¹³C-NMR, GPC and DSC. The copolymers were found to have the following characteristics: (1) Molecular weight distribution of the copolymer is rather narrow; (2) There exist only isolated propylene units distributed along the polymer chains even at propylene content as high as 14.9 mol%; (3) The distribution of ethylene sequence are not homogeneous. Insertion of propylene changes from 2,1-insertion in homopolymerization into 1,2-insertion when the preceding unit is ethylene.     

Copolymerization of 2-methyl-N-1,3-thiazole-2-ylacrylamide with glycidyl methacrylate: synthesis, characterization, reactivity ratios and biological activity

The free-radical copolymerization of 2-methyl-N-1,3-thiazole-2-ylacrylamide monomer (TMA) with glycidyl methacrylate (GMA) was carried out in 1,4-dioxane at 65 ± 1 °C using azobisisobutironitril (AIBN) as an initiator. The copolymers were characterized by FTIR, ¹³C-NMR and ¹H-NMR spectroscopic methods. The copolymer compositions were determined by elemental analysis. The weight-average and number-average molecular weights of the copolymers were obtained by gel permeation chromatography (GPC). The polydispersity indices of the polymers, determined with gel permeation chromatography, suggested a strong tendency for chain termination by disproportionation. Thermal properties of the polymers were also studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The monomer reactivity ratios were calculated according to the general copolymerization equation using Kelen–Tudos and Fineman–Ross linearization methods. The reactivity ratios indicated a tendency toward for alternation. The thermal decomposition activation energies of the polymers were evaluated by Ozawa method. The antibacterial and antifungal effects of the copolymers were also investigated on various bacteria and fungi. All the products showed moderate activity against different strains of bacteria and fungi.     

A simple one-step synthesis of unsaturated copolyesters

Copolyesters containing pendent vinylidine groups were prepared in a one-step synthesis by reacting either chloro- or bromoacetic acid with 2-(bromomethyl)acrylic acid and triethylamine in diethyl ether. Polymers were characterized by IR, ¹H- and ¹³C-NMR, DSC, and TGA. Copolymer formation supports a mechanism involving a triethylammonium carboxylate salt acting as an active nucleophilic species in a manner analogous to that seen in phase transfer catalysis involving carboxylate anions. Comparison of ¹³C-NMR spectra intensities indicates that 2-(bromomethyl)acrylic acid is much more reactive than the haloacetic acids leading to higher copolymer incorporation than in the monomer feed. Unsaturation in the copolymers provides a site for crosslinking during radical polymerization with an added vinyl monomer, similar to the way unsaturated polyesters function in commercial fiberglass formulations. This was confirmed by polymerization of both styrene and methyl methacrylate in the presence of an unsaturated copolymer giving insoluble semi-interpenetrating networks. These unsaturated copolymers are the first examples of soluble biodegradable glycolic acid polyesters containing such reactive functionality.     

Spontaneous copolymerization of N-(2-hydroxyethyl)ethyleneimine with isatoic anhydride

The polymerization of isatoic anhydride (electrophilic monomer) with N-(2-hydroxyethyl)ethyleneimine (nucleophilic monomer) was studied in the absence of added initiator at different feed monomer concentrations, temperature, and time of copolymerization. The copolymers were characterized by FT-IR, ¹H-NMR and ¹³C-NMR spectroscopy, and TGA. Based on spectroscopic data and copolymer composition, a copolymer structure was suggested. Received: 25 April 1997/Revised: 11 August 1997/Accepted: 14 August 1997