Estimation Of Molecular Weight Research Articles

Synthesis, self-assembly and surface-active properties of alkyl halide mediated imidazolium monomeric surfactants

Two imidazolium monomeric surfactants, that is, 1-tetradecyl-1H-imidazole [14IM] and 1-hexadecyl-1H-imidazole [16IM] has been synthesized and characterized by 1H NMR,13C NMR, FTIR, HRMS spectroscopies and thermogravimetric analysis (TGA) for number and types of protons and carbon, functional groups, estimation of molecular weight and thermal stability of these compounds. The conductivity was measured in double distilled water at four different temperatures, 288, 293, 298, and 303 K. The results showed that these surfactants behave as weak electrolytes. The density and viscosity data have shown the existence of strong interactions between imidazolium surfactants and solvent (water) molecules. The results obtained from Root’s equation indicate that surfactant–solvent interactions are important than surfactant–surfactant interactions in dilute solutions, that is, below critical micellar concentration. The values of constants obtained from Einstein and Moulik equations have revealed that there was stronger and significant interaction between imidazolium surfactants and water molecules below critical micellar region. The surface tension parameters have indicated that these surfactants are good contenders to lower the surface tension of air/water interface. The results obtained from surface tension data have shown that standard change in free energy of micellization (ΔG°mic) and adsorption (ΔG°ads) were negative, indicating that these surfactants molecules have spontaneous tendencies to form micelles in solution at higher concentration and to get adsorb at the air/water interface at lower concentration. The TGA has indicated good thermally stability and activation energy for thermal decomposition was found in the range of 37.26.26–98.20.20 kJ/mol.

Kinetic studies and bioremediation potential of chromate reductase-characterized Aspergillus flavus from tannery effluent

Chromium is among the major environmental pollutants endangering the health of all living things, including humans. Conventional methods for chromium detoxification are expensive, so bioremediation using fungi as potential agents for the detoxification of chromium is justified. This study aims to investigate chromium-resistant fungi capable of reducing or transforming Cr (VI) to less toxic Cr (III) from tannery effluents. The fungi were isolated from tannery wastewater and identified using 16S rRNA gene sequencing. Chromate reductase was isolated from pure fungal isolate and purified using molecular weight estimation and gel filtration chromatography. Aspergillus flavus, in an interesting turn of events, demonstrated 97% chromate reduction. The chromate reductase from Aspergillus flavus has KM of 0.015 mM and a Vmax of 0.25 mol/min. Furthermore, the enzyme's activity was constant at its peak at pH 7.0 and 50 oC, with a single band displaying a molecular weight of 44 kDa for a pure protein. The data suggest that A. flavus can be a good candidate for the detoxification of Cr (VI) in industrial effluents. The efficiency of which can be attributed to the action of chromate reductase in the A. flavus.

Comparative study on molecular and higher-order structures of legume seed protein isolates: Lentil, mungbean and yellow pea

Lentils and mungbean proteins are under-researched compared to pea and soybean. Lentils (green, red and black-lentils), mungbean and yellow pea protein isolates were obtained by alkaline extraction (pH 9)-isoelectric precipitation (pH 4.5) and investigated for molecular and higher-order structures using complementary and novel approaches. These extracted isolates showed comparable protein content but significantly greater nitrogen solubility index (NSI > 85 %) than commercial pea and soy protein isolates (NSI < 60 %). Based on molecular weight estimations from sodium dodecyl sulphate–polyacrylamide gel electrophoresis analysis, the soluble proteins of lentils and yellow pea were identified as legumin-like and vicilin-like, while mungbean was dominated by vicilin-like proteins. The soluble extracts were confirmed to be in native structural condition by size exclusion chromatography and nano-differential scanning calorimetry, unlike commercial extracts. Further differences in secondary structure were evident on circular dichroism spectra of the soluble extracts and deconvolution of the Amide I region (1700–1600 cm−1) from Fourier Transform Infrared of the total protein.

4-Aminoantipyrine Thiosemicarbazone Complexes with cobalt(II): Synthesis, Spectroscopic, Thermal, and Antibacterial Research

An interesting series of cobalt(II) complexes of the new ligands: The antipyrinethiosemicarbazones 4[N-(benzalidene) amino]antipyrinethiosemicarbazone (BAAPTS), 4[N-(2-hydroxy-benzalidene)amino]antipyrinethiosemicarbazone (2b), and 4[N-(2-hydroxy-1-naphthalidene)amino]antipyrinethiosemicarbazone (2c) The complexes were discovered to have the typical stoichiometry [CoX2(H2O)(L)] and [Co(L)2](ClO4)2, where X = Cl, NO3, NCS, or CH3COO, and L =2a, 2b, or 2c. Elemental analyses, molar conductivity measurements, molecular weight estimations, magnetic moments at room temperature, infrared, and electronic spectra were used to describe the complexes. The behaviour of each and every thiosemicarbazone is that of neutral tridentate (N, N, S) donor ligands. The perchlorate complexes are 1:2 electrolytes, but the chloro, nitrato, thiocyanato, and acetate complexes are essentially non-electrolytes, according to the conductivity measurements in PhNO2 solution. Studies on thermodynamic behavior were conducted for a few typical complexes, and a decomposition process was suggested. The cobalt(II) complexes of the ligands and their antibacterial and antifungal activities have also been studied, and it has been found that the complexes are more effective bactericides than the ligands.

Calibration of high performance size exclusion chromatography (HPSEC) for molecular weight estimation of aquatic humic substances

Three high performance size exclusion chromatography (HPSEC) columns were compared, along with mobile phase chemistry and calibration standards, for the determination of apparent molecular weight (AMW) of aquatic humic substances using a UV absorbance detector (λ = 254 nm). The addition of 10 % organic solvent did not influence peak elution times of sodium polystyrene sulfonate (PSS) standards or chromatograms of Suwannee River humic acid (SRHA) or fulvic acid (SRFA) but did result in an additional peak being detected in a treated municipal wastewater sample (WWT). Mobile phase concentration was found to have a greater effect on peak position of PSS standards and SRHA than mobile phase pH or sample injection volume. Several chemicals of known molecular weight were tested alongside PSS standards, with salicylic acid (138.1 Da) and 4-chlorobenzoic acid (156.6 Da) resulting in retention times that aligned with the PSS MW standards. Of the three columns tested, the two with comparable pore sizes (i.e., 250 and 300 Å) were found to result in similar peak elution times and highly linear calibration curves over the range of 210–17,000 Da, while the column with the smaller pore size (i.e., 100 Å) gave better peak separation in the low AMW range (i.e., < 1000 Da). Estimations of AMW of SRHA using various sets of calibration standards on one of the three columns tested ranged from 1080 to 2799 Da using 0.02 M NH4CH3CO2 as eluent and 60-µL injections. AMW of SRFA ranged from 939 to 2434 Da for the same conditions.

First-Order Prediction of the Relative Performance of Infrared (IR) Absorption, Raman, and Combined (IR + Raman) Spectroscopy for Estimating Composition and Bulk Properties of Fuel Mixtures

Using published infrared (IR) absorption and Raman scattering data for pure species, we performed simulations to gain insight into the performance of IR and Raman spectroscopy when applied to estimate the composition and properties of liquid mixtures. We also considered IR absorption applied to the evaporated mixtures. Using hypothetical mixtures composed of 237 pure species, we investigated estimation of molecular weight (MW) and density. Using hypothetical mixtures composed of 41 species, we investigated estimation of derived cetane number (DCN) and enthalpy of combustion (H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ) in addition to MW and density. For the 237-species problem, we found that Raman outperformed gas-phase IR by a factor of up to 1.6, and combined (Raman + gas-phase IR) spectroscopy outperformed Raman alone by a factor of up to 3.4. Similar trends were seen in the 41-species problem: for example, Raman was 1.2 times better for estimating DCN than gas-phase IR, and combined spectroscopy was 1.5 times better than Raman alone. We also estimated the performance for absorption in limited IR ranges: 600–1700 cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-{1}}$ </tex-math></inline-formula> (fingerprint region), 2650–3200 cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\text {-1}}$ </tex-math></inline-formula> (CH stretch region), and 3400–4500 cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\text {-1}}$ </tex-math></inline-formula> . The fingerprint region performed only 1.2–1.6 times worse than the full range (600–6500 cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\text {-1}}$ </tex-math></inline-formula> ), but the other ranges resulted in higher errors. For example, the CH stretch region performed 5–8 times worse. Gas-phase IR outperformed liquid-phase IR by a factor of up to 1.6 when using the full range.

Adsorption-Mediated Electrochemical Atomic Layer Deposition of Gold

Electrochemical atomic layer deposition (e-ALD) is an effective method for achieving atomic monolayer-by-monolayer deposition of metals. In this presentation, we will discuss the mechanistic events underlying gold (Au) e-ALD. The e-ALD process involves lead underpotential deposition (PbUPD) followed by spontaneous redox replacement (SLRR) of PbUPD by Au. During Au e-ALD, a unique three-stage mass transient is observed. Using voltammetry, electrochemical quartz crystal microgravimetry (e-QCM), and chronoamperometry, we present an in-depth study of the characteristics of this mass transient during Au e-ALD. Adsorption of Au+3-ligand complex(es) (Au-L) on the Au surface is shown to play a key role in the Au-ALD process. The adsorbed Au-L species are reduced in stage I while a PbUPD adlayer is formed. The SLRR of PbUPD adlayer by nobler Au occurs in stage II, followed by the re-adsorption of the Au-L species in stage III. A quantitative analysis of the deposit mass under different conditions allows estimation of the average molecular weight of the adsorbed Au-L complexes. Ramifications of such adsorption-mediated deposition to thickness uniformity, conformality and film roughness will be discussed. Figure 1

A comparison between analytical approaches for molecular weight estimation of proteins with variable levels of glycosylation.

Biotherapeutics, such as mAbs and fusion proteins, are a major and rapidly growing class of pharmaceuticals. Majority of the biopharmaceuticals are glycoproteins, wherein about 1 to 30% of their molecular weight (MW) are contributed by the glycans. Determination of MW of heavily glycosylated proteins, such as Fc-fusion proteins, is seriously hampered by the physicochemical characteristics and heterogeneity of the attached carbohydrates. Glycosylation influences the expected size of the glycoprotein, which leads to disproportionate MW estimation, in size-dependent methods. Hence, in this study, we have demonstrated the advantages and limitations of four widely used MW estimation techniques for three proteins having varying levels of glycosylation. It was proven that glycosylation had least impact on MW determination by SEC-MALS and SV-AUC. However, MW estimation by LC-MS and SDS-PAGE was extensively hampered by the degree of glycosylation. It is, thus, essential to consider the structural characteristics of proteins while selecting a technique for determining their MW.

Synthesis of high molecular weight L-Polylactic acid (PLA) by reactive extrusion at a pilot plant scale: Influence of 1,12-dodecanediol and di(trimethylol propane) as initiators

• Technical feasibility of using DDD and DTMP as initiators in the synthesis of PLA by using REX. • High molecular weight polymers with commercial properties are obtained. • FTIR, NMR and SEC methodologies have been applied for yield monitoring and molecular weight estimations. The present work describes the synthesis of polylactic acid (PLA) of isotactic high molecular weights via reactive extrusion ring-opening polymerization of L -lactide in presence of 1,12-dodecanediol (DDD) or di(trimethylol propane) (DTMP) as initiators. Weight-average molecular weights between 183 and 217 kDa were deduced by both diffusion NMR and SEC measurements. The functionality of each initiator allowed the obtention of PLA of linear multiarm branching with superior mechanical and rheological properties than those described in commercial references. PLA_DTMP demonstrated good performance in cast filming and PLA_DDD in injection molding. The reactive extrusion process presented herein has been validated in a relevant industrial environment and represents an interesting alternative to traditional synthesis methods with consequent cost savings.

Recent Progress in FD-LC-MS/MS Proteomics Method.

Through the course of our bio-analytical chemistry studies, we developed a novel proteomics analysis method, FD-LC-MS/MS (fluorogenic derivatization-liquid chromatography-tandem mass spectrometry). This method consists of fluorogenic derivatization (FD), LC separation, and detection/quantification of the derivatized proteins, followed by isolation, tryptic digestion of the isolated proteins, and final identification of the isolated proteins using electrospray ionization nano-LC-MS/MS of the generated peptide mixtures with a probability-based protein identification algorithm. In this review, we will present various examples where this method has been used successfully to identify expressed proteins in individual human cells. FD-LC-MS/MS is also suitable for differential proteomics analysis. Here, two biological samples are treated by the same steps mentioned above, and the two chromatograms obtained are compared to identify peaks with different intensities (variation in protein levels). Associated peak fractions are then isolated, and the differentially expressed proteins between the two samples are identified by LC-MS/MS. Several biomarkers for cancers have been identified by FD-LC-MS/MS. For more efficient separation, nano-flow LC with a phenyl-bonded monolithic silica-based capillary column was adopted for cell-expressed intact protein analysis. The derivatized human cell proteins (K562) and yeast cell (Saccharomyces cerevisiae) proteins as model intact cell proteins were analyzed by nano-flow LC with fluorescence detection. More than 1,300 protein peaks were separated/detected from both cells. For straightforward comparison of multiple peak separation profiles, a novel type of chromatogram display, termed the “spiderweb” chromatogram, was developed. A nano-LC-FD-LC-mass spectrometry trial for molecular weight estimation of FD proteins has also been conducted.

Dependence of intrinsic viscosity and molecular size on molecular weight of partially hydrolyzed polyacrylamide

AbstractAs a typical water‐soluble polymer, ultra‐high molecular weight (UHMW) partially hydrolyzed polyacrylamide (HPAM) has been widely used in various industries as thickeners or rheology modifiers. However, precise determination of its critical physical parameters such as molecular weight, radius of gyration (Rg) and hydrodynamic radius (Rh) were less documented due to their high viscosity in aqueous solution. In this work, the molecular structure of five UHMW‐HPAM samples with different MW was elucidated by 1H and 13C NMR spectroscopy, and their solution properties were characterized by both static and dynamic light scattering. It is found that all the second virial coefficient (A2) values are positive and approaching zero, indicating of a good solvent of 0.5 M NaCl for UHMW‐HPAM. The weight‐average molecular weight (Mw) dependence of molecular size and intrinsic viscosity [η] for these series of HPAM polymers with MW ranging from 4.81 to 15.4 × 106 g·mol−1 can be correlated as Rg = 3.52 × 10−2Mw0.51, Rh = 1.97 × 10−2Mw0.51, and [η] = 6.98 × 10−4 Mw0.91, respectively. These results are helpful in understanding the relationship between molecular weight and coil size of HPAM polymers in solution, and offer references for quick estimation of molecular weight and screening of commercial UHMW‐HPAM polymers for specific end‐users.

Improving SDS-PAGE method for monoclonal antibodies: The advantages of Tris-Acetate over Tris-Glycine SDS-PAGE system and comparison with CE-SDS method

Present study compares two different buffer systems for the electrophoretic separation of the IgG1 and IgG2 Monoclonal Antibodies using SDS-PAGE method. A modified Tris-acetate system was shown to be superior for separation of these proteins in a 6–20% gradient gel as compared with the traditionally used Tris-glycine method. This modified Tris-acetate buffer system showed sharper bands, more accurate determination of molecular weight, higher resolution, and better estimation of sub-fragments with closer results to those obtained by Capillary Gel Electrophoresis. Also in a parallel experiment, effect of IgG deglycosylation by PNGase-F enzyme was investigated and revealed no significant improvement on the SDS-PAGE results.

Part II: The influence of substrate type, film thickness, and primary ion type on molecular weight characterization of linear polydimethyl siloxane films by secondary ion mass spectrometry

In our previous paper, we showed that the molecular weight of linear, trimethyl‐terminated polydimethyl siloxane (PDMS) can be estimated using a standard curve by measuring PDMS endgroup‐related signal normalized to backbone‐related signal for PDMS films that are thick relative to the information depth of SIMS. Within industrial surface analysis laboratories, it is more likely that PDMS fluid is encountered as a thin film, perhaps as a contaminant or an additive that has exuded from a bulk material. This paper explores the influence of PDMS film thickness, substrate type, and primary ion projectile type (cluster vs. monoatomic) on the ratio of measured endgroup:backbone peak area ratio. These factors are shown to have a significant influence on the measured spectra, and these effects should be carefully considered before making molecular weight estimates of PDMS based on SIMS peak ratios.

A Surface Morphological Study, Poly(Vinyl Chloride) Photo-Stabilizers Utilizing Ibuprofen Tin Complexes against Ultraviolet Radiation

In this work, three Ibuprofen tin complexes were synthesized and characterized by Fourier Transform Infrared spectroscopy (FTIR), 1H and 119Sn-Nuclear Magnetic Resonance (NMR), and Energy Dispersive X-ray (EDX) spectroscopies to identify the structures. The complexes were mixed separately with poly(vinyl chloride) (PVC) to improve its photo-stability properties. Their activity was demonstrated by several approaches of the FTIR to exhibit the formation of new groups within the polymer structure due to the exposure to UV light. Moreover, the polymer’s weight loss during irradiation and the average molecular weight estimation using its viscosity before and after irradiation were investigated. Furthermore, different techniques were used to study the surface morphology of the PVC before and after irradiation. Field-emission scanning electron microscopy (FESEM) and optical microscope demonstrated that applying Ibuprofen tin complexes keeps the surface of PVC smoother, with fewer cracks and spots after irradiation comparing to the blank PVC. Finally, It seems possible that such synthesized Ibuprofen tin complexes can work as excellent photo-stabilizers of PVC. In particular, complex 1 showed the best results among other stabilizers due to the large conjugation system of the stabilizer.

Enhancing segmental compatibility and tuning the structure-property relationship in ferrocenylsilane tethered polyurethane

This article addresses the effect of enhanced segmental mixing on various physical properties of ferrocenylsilane tethered polybutadiene based polyurethane (PU). To study this, 2-(ferrocenylpropyl) dimethylsilane (FPDS) has been grafted to the pendant vinyl double bond of hydroxyl terminated polybutadiene (HTPB) and 2, 4-dinitrobenzene attached HTPB (HTPB-DNB) through hydrosilylation reaction and then this resulting diols (FPDS-g-HTPB and FPDS-g-HTPB-DNB) were polymerized with isophorone diisocyanate (IPDI) to obtain FPDS-g-HTPB-PU and FPDS-g-HTPB-DNB-PU. Spectral (NMR, IR) analysis, molecular weight measurements and estimation of free hydroxyl contents were carried out to confirm the formation of these new diols. The careful variation of the grafting condition altered the extent of FPDS tethering on the diols which resulted varying amount of Si and Fe contents in these modified HTPBs. Density functional theory (DFT) calculation revealed the presence of various interactions of Si with various functionalities including ferrocene of the chain which resulted highly cross-linked polymer matrix. Cyclic voltammetry (CV) measurements of FPDS-g-HTPB-DNB displayed non-Nerstain reversible redox system with slow electron transfer process owing to the presence of DNB. Further, the PUs obtained from these HTPBs were prepared and characterized thoroughly in terms of thermal, mechanical, structural and tensile properties to study the segmental mixing between hard and soft segments of PUs owing to the presence of Si, Fe and DNB in the PU chain. Higher degree of segmental mixing was noticed when Si, Fe in the diol increased and also presence of DNB in the diol played a significant role in inducing the segmental mixing. The co-existence of segmental mixing and phase separation has been confirmed by small-angle x-ray scattering studies which further reaffirmed by FESEM analysis. Finally, composite solid propellants (CSPs) were prepared from these modified HTPBs and burn rate measurements were carried out. We found that CSPs obtained from FPDS-g-HTPB-DNB displayed ~10% higher burn rate than the CSP made from bare HTPB-DNB.

Biochemical characterization of endoglucanases produced by Myceliophthora thermophila M.7.7 in solid-state culture

Cellulases have been investigated for their potential application in lignocellulosic residues, used to produce second-generation ethanol (2 GE), as these enzymes can hydrolyze cellulose and release glucose for alcoholic fermentation by yeasts. The aim of this project was to characterize the endoglucanases produced by the thermophilic fungus Myceliophthora thermophila M.7.7 in solid-state cultivation. Tests were carried out with the crude enzyme extract (CEE) to assess the effects of pH, temperature, and various chemicals including cations and phenolic compounds on endoglucanolytic activity. The molecular weight estimation was performed by polyacrylamide gel electrophoresis (SDS-PAGE), and it was possible to observe seven endoglucanases detected by zymography, with estimated Mw in the range between 26 and 82 kDa. The optimum pH for the CEE was 5.5 and the optimum incubation temperature was 70 °C. Concerning endoglucanase stability, the highest activities were achieved in the pH range of 6.0–6.5, and between temperatures of 30 and 40 °C up to 120 min. Among the tested reagents, Triton, dithiotreitol (DTT), and Isopropanol increased the enzymatic activity on the crude extract by about 10%. Among cations, only Sr2+ significantly increased the endoglucanases’ activity. Of the phenolic compounds, although all induced a decrease of the endoglucanolytic activity, none could nullify it after a pre-incubation for 24 h. The apparent kinetic parameters were determined using carboxymethylcellulose (CMC), being Vmax = 51.7 ± 2.7 μmol min−1 and Km = 0.99 ± 0.15 g% CMC (9.9 mg mL−1).

Angiotensin Converting Enzyme Inhibitory Activity of Blue Lupin (Lupinus angustifolius) Proteins

Abstract Objectives To evaluate the ACE inhibitory activity of protein hydrolysates derived from lupin Methods Methods used are spectrophotometer to assay the ACE activity, electrophoresis for estimation of protein molecular weight, and HPLC for determining products of ACE activity. Results The results revealed that the lupin flour was abundant in protein (43.3 g/100 g). Results from sequential Osborne extraction procedure showed that lupin protein comprised of 46% salt-soluble globulin, 27% water-soluble albumin, 18% alkaline-soluble glutelin and 7% alcohol-soluble prolamin fractions. Furthermore, lupin protein was rich in lysine but limiting in methionine. Hydrolysates prepared using Alcalase exhibited higher ACE inhibitory activities compared with those prepared using Flavourzyme, showing IC50 values ranging from 0.10 to 0.21 mg/mL. However, there was no significant difference in IC50 values between the hydrolysates prepared using Alcalase for 4, 10 and 16 h of hydrolysis times. Conclusions The results suggested that globulin was the major contributing protein fraction on ACE inhibitory effect in lupin protein. The lupin protein hydrolysates with potent ACE inhibitory activities can be incorporated into the daily diet to prevent hypertension. Funding Sources Ministry of Education Malaysia.

Purification and Characterization of D-psicose 3 Epimerase (DPEase) From Escherichia coli BL21 (DE3) pET21b dpe.

The DPEase enzyme from Agrobacterium tumefaciens is more efficient and has a high activity in D-fructose. The dpe gene has been successfully cloned to Escherichia coli BL21 (DE3) pET-21b dpe but the enzyme has not been purified and its character is unknown. The intent of this study was to purify and assign of DPEase enzyme by recombinant E. coli. The enzyme was clarified by affinity chromatography and then characterized by following pH, temperature, co-factor parameters. Analysis of molecular weight proteins was done by SDS-PAGE. Through purification, the purified DPEase activity was increased 1,01 times than crude and with 84.2% of yield. The DPEase had an the maximum temperature is 40°C and pH was 8.5. The presence of Mg2+, Mo2+, Cu2+, Ca2+ and Zn2+ inhibited the activity of the enzyme while of Co2+, Mn2+, Fe2+, Ni2+ enhanced the activity. Estimation of molecular weight through SDS-PAGE revealed that weight of DPEase was 32 kDa. Purified DPease enzymes shows clear bands that demonstrate successful purification using affinity chromatography. It is expected that after pure enzymes are obtained the character of the enzymes working will be maximized.

Structural relaxation and glass transition in high-solid gelatin systems crosslinked with genipin

Structural relaxation and glass transition were examined in the swelling behaviour of a high-solid biopolymer matrix; genipin-crosslinked gelatin. Degree of swelling was quantified by the Flory-Rehner theory that furnishes estimates of average molecular weight between crosslinks and network mesh size. Fourier transform infrared spectroscopy and wide angle X-ray diffraction described intermolecular interactions and the extent of amorphicity in the crosslinked matrix. Micro differential scanning calorimetry provided evidence of the changing thermodynamic characteristics of the gelatin network in the presence of the crosslinker. Modulated differential scanning calorimetry and small deformation oscillatory rheology unveiled the vitrification properties of the system. Experimental measurements were treated with the time-temperature superposition principle to unveil an extensive master curve through the rubbery, glass transition and glassy states. Viscoelastic behaviour was modelled with the combined predictions of the modified Arrhenius and William-Landel-Ferry theories to pinpoint the mechanical glass transition temperature that was compared with predictions from calorimetry. Comprehensive understanding of polymeric behaviour during swelling affords greater control in the design of targeted delivery matrices for drugs and other bioactive compounds.

Extension of the Concept of Intrinsic Viscosities to Arbitrary Polymer Concentration: From [η] via {η} to Intrinsic Bulkiness

The capabilities of an alternative definition of intrinsic viscosities [η] published some years ago is being studied by means of comprehensive viscometric data reported in the early days of polymer science. It introduces the generalized intrinsic viscosity {η} as the specific hydrodynamic volume at arbitrary polymer concentration c. {η} quantifies the size of the flow unit and decreases monotonously for T ≫ Tg (glass transition temperature) as a function of c but passes a pronounced minimum as T approaches Tg. In the limit of the pure polymer melt, {η} becomes ; this newly introduced property is termed intrinsic bulkiness, by analogy to the intrinsic viscosity, and provides noncalorimetric experimental access to Tg; it also allows estimates of entanglement molecular weights based on the Newtonian flow behavior. Moreover, the molecular weight dependence of provides information on the contributions of endgroups to the flow behavior.