Synthesis and characterization of the new cellulose derivative films based on the hydroxyethyl cellulose prepared from “Stipa Tenacissima” cellulose of Eastern Morocco. I. Solubility study

Hydroxyethyl cellulose Acetate (HECA) was prepared starting from hydroxyethyl cellulose (HEC), acetic anhydride and perchloric acid which was used as catalyst. The synthesized product was characterized by FTIR, ¹³C NMR, and ¹H NMR. Substitution degree (DS) of HECA was determined using FTIR spectra taking a classical titration method as reference. The ¹H NMR spectroscopy was also used to confirm the results obtained by FTIR. The DS is substantially affected by the temperature, the time of reaction and especially the equivalent number (eq. nb.) of the acetic anhydride added. We have studied and discussed in the context of usage in modification reactions, the solubility of the HECA samples by varying their DS. This investigation was based on the determination of the Flory‐Huggins interaction parameters (χ_SP) using the partial Hansen solubility parameters (HSP). HSP of HEC and the HECA samples were calculated from the Van‐Krevlen‐Hoftyze (VKH) method and the T. Lindvig approximation. We have focused our work on predicting and controlling family solvents of HECA with various DS, to facilitate and to optimize the homogenous modification reaction conditions. From results on a range of HECA samples, it is conclude that their prediction solubility taking the value of DS into account is possible, and then the surface modification can relatively be easily realized. The thermal analysis study shows some differences in T_g and thermal degradation between HEC and HECA, moreover these thermal temperatures are influenced by DS values. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

NMR and FT Raman characterisation of regioselectively sulfated chitosan regarding the distribution of sulfate groups and the degree of substitution

Chitosan sulfates (CHS) were prepared with chlorosulfonic acid homogeneously and non-homogeneously. The total degrees of substitution (DS) ascribed to sulfate groups (DS_S) were determined with elemental analysis and the partial DS at 6-O-position was estimated via ¹³C NMR. CHS with diverse total DS_S and sulfation patterns were obtained according to the analysis. The effects of selected reaction parameters that can influence the distribution of sulfate groups were examined. The structure of CHS was then characterized with various NMR techniques, i.e. one- (1D-) and two-dimensional (2D-) NMR, and FT Raman spectroscopy. It was found that the primary hydroxyl groups were always predominantly sulfated for CHS prepared under homogeneous or non-homogeneous conditions and no sulfate groups at 2-N-position could be detected. Finally, the feasibility of using FT Raman spectroscopy as another alternative for determining the total DS_S of CHS was presented.     

Synthesis and characterization of carboxymethylated red angico (Anadenanthera macrocarpa) exudate polysaccharide

Red angico is a heteropolysaccharide (arabinogalactan) obtained from Anadenanthera macrocarpa trees. Carboxymethylation of angico gum (AG) with monochloroacetic acid (MCA) in alkaline aqueous medium resulted in samples which were characterized by ¹³C nuclear magnetic resonance spectroscopy and gel permeation chromatography. The effects of reaction parameters, such as alkali concentration, MCA/AG ratio and temperature on the reaction yield and degree of substitution (DS) were investigated. The DS and MCA total efficiency values increase up to 2 h reaction time and then decrease. The DS varied from 0.11 to 1.10 depending on NaOH/MCA/AG ratio and temperature. The highest MCA total efficiency (0.57) was obtained for NaOH/MCA/AG molar ratio equal to 3:1:1, at 70°C. (DS = 0.63, yield = 91.0%). Nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC) analysis shows that polymer degradation was observed in all samples. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2985–2991, 2007     

Degree of sulfonation and microstructure of post-sulfonated polyethersulfone studied by NMR spectroscopy

Commercial polyethersulfone (Udel^® 1800) based on 4,4′-dihydroxy-2,2-diphenylpropane (bisphenol-A) and dichlorodiphenylsulfone was post-sulfonated using trimethylsilyl chlorosulfonate under mild conditions. The partially sulfonated polyethersulfones were investigated by ¹H and ¹³C NMR in their acid and/or sodium salt form. Several ¹³C NMR signals could be assigned up to the triad level. ¹³C-T₁ relaxation times were determined by the inversion recovery method for all carbons to ensure conditions for quantitative ¹³C NMR measurements. Additionally, the nuclear Overhauser enhancements are given. The degree of sulfonation (DS) of the samples covers the range from 13.6 to 100% as determined both by ¹H and ¹³C NMR spectroscopy. The NMR spectra confirm that the sulfonation occurs solely as mono-substitution of each phenyl ring of the dioxy-2,2-diphenylpropane unit in ortho-position to the ether bond. The microstructure of all polymers was evaluated from the content of dioxy-2,2-diphenylpropane-based diads and diphenylsulfone-centred triads. From the development of non-, mono- and disulfonated dioxy-2,2-diphenylpropane units with increasing DS it can be concluded that the sulfonation of the first phenyl ring retards the sulfonation of the second one. Thus, the non-sulfonated units deplete faster and the monosulfonated units are enriched compared with a random sulfonation. There is no reactivity influence between dioxy-2,2-diphenylpropane units which are separated by a diphenylsulfone unit because the content of diphenylsulfone-centred units follows the random distribution.     

Lignins as macromonomers for polyurethane synthesis: A comparative study on hydroxyl group determination

The hydroxyl group contents of four technical lignins [Indulin AT (Meadwestvaco), Alcell (Repap), Curan 27‐11P (Borregaard LignoTech), and Sarkanda (Granit SA)] were investigated in view of their valorization as polyols in polyurethane synthesis. The different hydroxyl group contents were determined by the following methods: titration and ¹H‐NMR, ¹³C‐NMR, and ³¹P‐NMR spectroscopy. The titration method chosen was on the basis of a standard method commonly used to characterize commercial polyols for polyurethanes synthesis. The values of the total and phenolic hydroxyl contents determined by the different techniques were found to be in good agreement. For the total hydroxyl contents, coefficients of variation of 5.6% (Alcell), 3.2% (Indulin AT), 2.3% (Sarkanda), and 6.2% (Curan 27‐11P) were established. For the phenolic hydroxyl contents, a good correlation was observed between data obtained from ³¹P‐NMR and ¹³C‐NMR for all lignin samples, except for the Sarkanda lignin, for which a relatively high coefficient of variation (12.6%) was found. For softwood lignins (Indulin AT and Curan 27‐11P), the phenolic hydroxyl content determined by ¹H‐NMR was always lower than that deduced from ³¹P‐NMR and ¹³C‐NMR spectroscopy. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Comparison of two synthesis methods on the preparation of Fe,N-Co-doped TiO2 materials for degradation of pharmaceutical compounds under visible light

In this work, we report the synthesis, characterization and photocatalytic evaluation of visible light active iron-nitrogen co-doped titanium dioxide (Fe³⁺-TiO_2−xN_x) nanostructured catalyst. Fe³⁺-TiO_2−xN_x was synthesized using two different chemical approaches: sol-gel (SG) and microwave (MW) methods. The materials were fully characterized using several techniques (SEM, UV–Vis diffuse reflectance DRS, X-ray diffraction XRD, and X-ray photoelectron spectroscopy XPS). The photocatalytic activity of the nanostructured materials synthesized by both methods was evaluated for the degradation of amoxicillin (AMX), streptomycin (STR) and diclofenac (DCF) in aqueous solution. Higher degradation efficiencies were encountered for the materials synthesized by the SG method, for instance, degradation efficiencies values of 58.61% (SG) and 46.12% (MW) were observed for AMX after 240 min of photocatalytic treatment under visible light at pH 3.5. With STR the following results removal efficiencies were obtained: 49.67% (SG) and 39.90% (MW) at pH 8. It was observed the increasing of degradation efficiencies values at longer treatment periods, i.e., after 300 min of photocatalytic treatment under visible light, AMX had a degradation efficiency value of 69.15% (MW) at pH 3.5, DCF 72.3% (MW) at pH 5, and STR 58.49% (MW) at pH 8.     

Synthesis and characterization of long-chain fatty acid cellulose ester (FACE)

Long-chain fatty acid cellulose esters (FACE) were synthesized by the acid chloride-pyridine reaction with different degrees of substitution (DS). The hydrolyzed soybean oil was used as unsaturated fatty acids, its unsaturation degree, and composition were analyzed by ¹H and ¹³C NMR methods. The chemical structures of FACE were confirmed by solid-state ¹³C NMR, and substitution reaction of fatty acid chloride on cellulose were analyzed by IR spectroscopy. FACE(s) are insoluble in common organic solvents, such as benzene, toluene, THF, etc., at refluxing temperature. As the DS increased, the tensile strength of extruded FACE films decreased, but elongation increased. © 1994 John Wiley & Sons, Inc.     

Cationic polyelectrolytes from natural building blocks of chitosan and inulin

Novel chitosan-N-inulin graft copolymers with different degree of substitution (DS) of chitosan were synthesized via water-soluble 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide mediated reaction. Chemical structure and composition of the chitosan derivatives was confirmed by chemical analysis, FT-IR, XPS, ¹H and ¹³C NMR spectroscopy, and potentiometry. Chitosan–inulin copolymers were high-molecular-weight hydrophilic products soluble in water in a wide pH range forming extraordinary viscous solutions. Intrinsic viscosity of N-modified chitosans was sharply suppressed by added electrolyte and had tendency to decrease at higher DS of chitosan. pK_α values of the chitosan–inulin copolymers determined from potentiometric titration data using Henderson–Hasselbalch equation were in the range 6–7 slightly increasing at higher DS. Novel water-soluble chitosan copolymers retained cationic properties of chitosan and could be used as surface conditioners.     

Identification of Turkish extra virgin olive oils produced in different regions by using NMR (1H and 13C) and IRMS (13C/12C)

Isotope ratio mass spectroscopy (IRMS) and nuclear magnetic resonance (NMR) spectroscopy techniques are two of the analytical methods that are used to characterize food products. The aim of this study is to classify extra virgin olive oil (EVOO) samples collected from different regions of Turkey based on ¹H and ¹³C NMR spectra along with IRMS δ¹³C carbon isotope ratio data by using chemometrics multivariate data analysis methods. A total of 175 EVOO samples were analyzed in 2014/15 and 2015/16 harvest seasons. Multivariate classification and clustering models were used to identify geographical and botanical origins of the EVOOs. IRMS results showed that there was no significant difference in terms of δ¹³C values between the years in terms of harvest year (p > 0.05), only extraction phase and variety were statistically significant factors (p < 0.05). The interactions of the factors showed that the harvest year × variety interaction is important. The outcomes of this research clearly indicated that considering the partial least squares discriminant analysis result with NMR spectra, the percent success of the model in the South Marmara, North Aegean, and South Aegean region samples were 95%, 95.7%, and 96.4% in the model set, respectively. The results showed that by using classification and clustering models, geographic marking and labeling of these oils can be carried out regardless of differences in year and production systems (2 and 3 phase extraction system) according the NMR analysis.     

Morphology and molecular mobility of plasticized polylactic acid studied using solid‐state 13C‐ and 1H‐NMR spectroscopy

MAS ¹³C‐NMR measurements were used for the study of morphology and molecular mobility in amorphous quenched and triacetine‐plasticized PLA samples and PLA samples which underwent cold crystallization during annealing at 80 and 100 °C. The single pulse MAS ¹³C‐NMR spectra indicate that plasticizer promotes cold crystallization which results in the decrease of the temperature of crystallization and formation of more perfect crystalline domains. The T₁(¹³C) spin‐lattice relaxation times show that the presence of plasticizer molecules leads to an increase of local mobility in PLA chains but plasticized PLA after annealing at 100 °C shows more rigid structure. The series of broad line ¹H‐NMR spectra performed at temperatures up to 100 °C provided information on the changes in relaxation processes and morphology of the studied samples. The interpretation of the results obtained using the techniques of NMR spectroscopy were supported by WAXD and DSC measurements. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43517.     

CP/MAS C NMR analysis of the structure and hydrogen bonding of melt-crystallized poly(vinyl alcohol) films

The structure and hydrogen bonding of the melt-crystallized atactic poly(vinyl alcohol) (A-PVA) films, which were carefully prepared without significant thermal degradation, have been characterized by CP/MAS ¹³C NMR spectroscopy. The ¹³C spin-lattice relaxation analysis has revealed that there exist three components with different T_1C values, the crystalline, less mobile noncrystalline and mobile noncrystalline components, in good accord with the results for different PVA samples previously reported. It should be noted that the T_1C values of the crystalline and noncrystalline components are appreciably smaller for the melt-crystallized films than those for the un-annealed and annealed samples prepared by casting from the aqueous solution. The ¹³C NMR spectra of the crystalline and noncrystalline components are separately recorded by using the difference in T_1C and their CH lines are successfully resolved into three and seven constituent lines by the least-squares curve fitting, respectively. Moreover, the statistical analysis of the integrated intensities of the constituent lines thus obtained enables to determine the probability f_a for the formation of intramolecular hydrogen bonding in the successive two OH groups along each chain and another probability f_t of the trans conformation for the crystalline and noncrystalline components. It is found that the f_a value is relatively larger for the melt-crystallized films than those for the un-annealed and annealed samples. On the basis of these results, the features of the melt-crystallization and the resulting crystalline-noncrystalline structure are discussed by particularly considering effects of intra- and inter-molecular hydrogen bonding on the crystallization.     

Unconventional Synthesis of Pullulan Abietates

Pullulan abietic acid esters (pullulan abietates) of different degree of substitution (DS) were synthesized homogeneously in N,N-dimethylacetamide using differently in situactivated abietic acid derivatives. In situ activation was achieved with p-toluenesulfonyl chloride, N,N‘-carbonyldiimidazole and iminium chloride formed from oxalyl chloride/N,N-dimethylformamide. The DS values of the biopolymer esters determined by acid-base titration after saponification indicated that in situ activation with p-toluenesulfonyl chloride is most efficient while in case of the in situ activation with N,N‘-carbonyldiimidazole almost no polymer degradation occured. The pullulan abietates were characterized by elemental analysis, GPC, FTIR-, ¹H- and ¹³C NMR spectroscopy.     

Nucleophilic displacement reactions on tosyl cellulose by chiral amines

Summary New 6-deoxy-6-amino cellulose derivatives with a degree of substitution (DS) in the range from 0.4 to 0.6 were synthesized by nucleophilic displacement (S_N) reactions of cellulose tosylates (DS_Tos 0.74 and 1.29) with R(+)-, S(−)- and racemic 1-phenylethylamine under homogeneous conditions in N,N-dimethylformamide and water. The structure of the polymers was characterized by elemental analysis, FTIR and ¹³C NMR spectroscopy. The DS values obtained as well as the optical rotation and circular dichroism measurements in dimethyl sulfoxide reveal that the initial chirality of the cellulose backbone does not have any significant influence on its reactivity with either of the two enantiomeric amines. Received: 21 September 2000/Accepted: 5 January 2001     

Synthesis of cationic hemicellulosic derivatives with a low degree of substitution in dimethyl sulfoxide media

A series of water‐soluble cationic 2‐hydroxylpropyltrimethylammonium hemicellulosic derivatives with low average degrees of substitution (DS's) were prepared by the incorporation of the cationic moiety 2,3‐epoxypropyltrimethylammonium chloride (ETA) onto the backbone of hemicelluloses in the presence of NaOH as a nucleophilic catalyst in homogeneous dimethyl sulfoxide (DMSO) media. The dependence of the homogeneous reaction on the different affecting factors was investigated. The average DS was calculated from the N/C ratio in the products and from the weight gain. The degree of substitution determined by the nitrogen content (DS_N) values up to 0.25 in a one‐step synthesis of the etherified hemicelluloses could be controlled by the adjustment of the amount of solvent used and the molar ratio of NaOH or ETA to the anhydromonomer units in the hemicelluloses. The structure of the cationic hemicellulosic derivatives formed was determined by Fourier transform infrared spectroscopy and further confirmed with solution‐state ¹³C‐NMR spectroscopy. In comparison, no significant degradation of the hemicellulosic derivatives occurred during the etherification of the polymers in the homogeneous DMSO system. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Structure–property correlation study of hyperbranched polyurethane–urea (HBPU) coatings

This paper deals with the structure–property relation of different HBPU coatings based on the variation of parameters like, NCO/OH ratio, generation number and type of diisocyanates used. For this, the NCO terminated HBPU prepolymers were synthesized first by reacting the different generation hyperbranched polyesters (HBPs) with excess diisocyanates. In the next step, these HBPU prepolymer coated films were completely moisture cured to get the desired HBPU coatings. The synthesized polymers were confirmed by ¹H, ¹³C NMR and FT-IR spectroscopy methods whereas structure–property relation was drawn from the FT-IR peak deconvolution technique. The degree of branching (DB) and percent composition of different structural units present in the HBPs were calculated from the ¹H and ¹³C NMR data by using Fretch equation. The melt viscosity study of different HBP samples suggests that most polyester sample showed Newtonian behavior. The coating film properties were studied by DMTA, TGA, UTM, and contact angle measurement instruments. DMTA and TGA data shows that the increase of NCO/OH ratio and generation number had a favorable impact on storage modulus (E′), glass transition temperature (T_g), onset degradation temperature (T_1ON) and char residue values of the coatings. The contact angle and UTM data suggest that the hydrophobicity and tensile strength increases but flexibility decreases with increasing the NCO/OH ratio.     

Thermal oxidative and photo‐oxidative degradation of polytetrahydrofuran studied using 1H NMR, 13C NMR and GPC

The products and mechanism of the thermal oxidative degradation at 180 °C and the photo‐oxidative degradation at 40 °C of polytetrahydrofuran have been investigated using ¹H NMR, ¹³C NMR and GPC. The NMR analysis was assisted by the use of DEPT ¹³C spectra, two‐dimensional NMR spectroscopy (COSY, HMQC and HMBC) and chemical shift simulation software. The NMR spectra of both thermally and photolytically degraded samples were similar showing that the degradation mechanisms were similar. GPC indicated that both chain scission, leading to lower molar mass products, and chain extension, leading to higher molar mass products, occurred initially. NMR analysis of the initial soluble degraded polymers showed that chain scission resulted in formate, aldehyde, propyl ether, butyl ether and propanoyl chain ends, and in‐chain ester groups were also formed. For longer periods of degradation, crosslinked gels were formed but these were not amenable to detailed structural characterisation by high‐resolution NMR to determine the crosslink mechanism. Copyright © 2004 Society of Chemical Industry     

Solid-state C NMR analyses of the structures of crystallized and quenched poly(lactide)s: Effects of crystallinity, water absorption, hydrolytic degradation, and tacticity

The effects of crystallinity, water absorption, hydrolytic degradation, and tacticity on the solid structure and chain mobility of poly(lactide)s were investigated by solid-state ¹³C NMR spectroscopy. The following results were obtained from the line shapes of the carbonyl and methine carbons in ¹³C NMR spectra and their spin-lattice relaxation behavior. The crystallized poly(l-lactide) (PLLA) specimens in the dried, hydrated, and hydrolyzed states had two components, rigid and mobile components which can be, respectively, assigned to the crystalline and non-crystalline components. Upon water absorption, the chain mobility in the non-crystalline component of PLLA-C remained unvaried, reflecting a very small effect of the incorporated water molecules at room temperature. In contrast, the elevated chain mobility in the crystalline component and unclear splitting of carbonyl carbon strongly suggest that the water molecules are incorporated in the crystalline lattice. Upon removal of the non-crystalline components by hydrolytic degradation of crystallized PLLA, the chain mobility was slightly elevated in both crystalline and non-crystalline components by the lowered crystalline thickness and shortened non-crystalline chains. The non-crystalline specimens, PLLA (PLLA-Q) and poly(dl-lactide) (PDLLA), could be analyzed to contain two components, rigid and soft components, with the similar conformation but different restricted states of chains which cause high and low chain mobility. The insignificant difference in the spectral shapes and T_1C values between PLLA-Q and PDLLA strongly suggests that the effects of difference in the chain regularity and interaction on the spectral shapes and T_1C values are very low.     

Synthesis and Characterization of GAP-PEG Copolymers

ABSTRACT

A series of glycidylazide–poly(ethylene glycol) (GAP-PEG) copolymers were synthesized by cationic ring-opening polymerization of epichlorohydrin (ECH) in the presence of poly(ethylene glycol) (PEG) using borontrifluoride etherate (BF₃-etherate) as catalyst, followed by the conversion of the CH₂Cl groups of poly(epichlorohydrin) (PECH) to CH₂N₃ groups. The formation of PECH-b-PEG-b-PECH triblock copolymers was confirmed by IR, ¹H NMR, and ¹³C NMR spectroscopy. The corresponding GAP-b-PEG-b-GAP triblock copolymers were characterized by UV, IR, ¹H NMR, and ¹³C NMR spectroscopy. The copolymers have shown an increment in their molecular weights as the higher analogue molecular weight PEGs were used in the polymerizations. The thermogravimetry-differential thermogravimetry (TG-DTG) and differential scanning calorimetry (DSC) studies of the GAP triblock copolymers indicate an increase in the decomposition temperature of the azide groups of GAP block in the copolymers caused by the introduction of higher molecular weight PEG blocks. GAP-PEG copolymers have shown lower glass transition temperatures than the homo glycidylazide polymer. The nitrogen content of the GAP-PEG copolymers was estimated by various methods and the value was in good agreement with the estimated values.     

Analysis of Lignins as Propionate Derivatives by NMR Spectroscopy

Lignin propionates were prepared by treating lignin samples with propionic anhydride in pyridine solution and the derivatives obtained were examined by NMR spectroscopic methods. ¹H NMR spectroscopy of lignin propionates offers a possibility to determine the number of hydroxyl groups based on the methyl proton signal (δ ～ 1.2) as well as the methylene proton signal (δ ～ 2.5) of the propionate groups. It was found to be advantageous to use propionate derivatives for the analysis of hydroxyl groups in lignin products exhibiting signals (from >CH- and -CH₂- groups) that interfere with the acetate group signals. Analysis of ester groups by ¹³C NMR spectroscopy gave practically the same results as those earlier reported for acetate derivatives.     

Study on the Azido‐Tetrazolo Tautomerizations of 3,6‐Bis(azido)‐1,2,4,5‐tetrazine

The azido‐tetrazolo tautomerizations of 3,6‐diazido‐1,2,4,5‐tetrazine (DIAT) in different solvents were investigated with HPLC and ¹³C NMR spectroscopy. 6‐Amino‐tetrazolo[1,5‐b]‐1,2,4,5‐tetrazine (ATTZ) was irreversibly formed as the final product by azido‐cyclization following N₂ elimination from one of the azido substituents at room temperature in DMSO. The structure of ATTZ was characterized by X‐ray crystallography; differential scanning calorimetry (DSC), mass spectrometry, as well as IR and ¹H NMR and ¹³C NMR spectroscopy. The crystal density was found to be 1.272 g cm⁻³. DSC result suggested that ATTZ with the melting point of 84 °C strongly decomposes with explosion at 198 °C, which can be regarded as a primary explosive.