Dynamic fourier transform infrared spectroscopy of liquid-crystalline elastomers

The influence of mechanical deformation on the orientation behaviour of the phenyl benzoate mesogenic groups in polyacrylate- and polymethacrylate-based liquid-crystalline (l. c.) elastomers with spacers of six methylene units is investigated as a function of temperature and time by means of linear-dichroism infrared spectroscopy. The mesogens in the polymethacrylate elastomers preferably align perpendicular to the stretching direction and show a biaxial phase with homeotropic orientation. The changes in sample geometry, especially the film-thickness variation during deformation, are studied. The orientation behaviour of the mesogens in the polyacrylate elastomers is different in the nematic and smectic phase. On stretching, the mesogens align parallel in the nematic and perpendicular to the stretching direction in the smectic phase. The orientation of a film stretched in the smectic phase, however, changes to be parallel to the stretching direction if its temperature is raised once above the smectic-to-nematic transition temperature. The dynamics of reorientation of the mesogens strongly depends on temperature. With high mobility of the mesogens no phase lag between deformation and orientation can be detected on a timescale of 100 ms. The orientation behaviour of l. c. elastomers is very complex and depends on many parameters, each of which is important.     

Stopped-flow fourier transform infrared studies in polymer chemistry

The application of stopped-flow FT-IR spectroscopy to group transfer polymerization (GTP) and cyclic oligomeric carbonate formation is described. The influence of catalyst structure, propagating end stereochemistry and degree of polymerization (DP) on the rate of monomer addition was examined for GTP. Also, the major GTP termination process was identified and characterized. Model reactions were used to study the kinetics of acyl ammonium salt formation and subsequent conversion to urethane. These results were used to further develop the mechanism of bisphenol A-bischloroformate macrocyclization.     

Photoinitiated cross-linking of silicones, 10. Photoinitiated cross-linking of silicone acrylates as studied by fourier transform infrared spectroscopy

The photoinitiated cross-linking of silicone acrylates is studied by FT-IR spectroscopy. The influences of light intensity, exposure time and type of photoinitiator are described. The parameters of the kinetic equation are determined. It is shown that oxygen acts as an inhibitor. The asymmetric C?O stretching IR band of the uncross-linked and cross-linked system can be separated into two bands which are attributed to different conformations and geometric arrangements of the acrylate groups, respectively.     

Evaluation of in vivo adsorption of blood elements onto hydrogel-coated silicone rubber by scanning electron microscopy and fourier transform infrared spectroscopy

Three hydrogel formulations consisting of 2-hydroxyethyl methacrylate (HEMA) copolymerized with N-vinyl pyrrolidone (NVP) were incorporated into silicone rubber by irradiation-induced polymerization. These coatings were chosen to represent different degrees of hydrophilicity, and they changed the hydrophobic character of the silicone rubber surface to that of hydrophilic. These composite materials and the silicone rubber comparison material were used as femoral artery-to-vein (A-V) shunts and were removed at 15 min, an approximate time representative of an initial buildup stage of blood elements on test surfaces. Data obtained by scanning electron microscopy (SEM) were used to determine the type and amount of adhering blood cells and fibrin at the time interval described. One-half of each specimen was used for Fourier Transform Infrared (FT-IR) analysis to provide a direct comparison of the relative amounts of protein present on the silicone rubber and the three hydrogel composite samples. The combined SEM and FT-IR analyses were performed on A-V samples from three dogs. Differences in the response of blood to the surfaces were found by the combined SEM and FT-IR analyses. The more hydrophilic a hydrogel grafted surface, the less fibrin and cellular elements were seen deposited on it. This is not interpreted as an indication of less reactivity, but is more likely due to thrombus buildup and a degree of subsequent embolization (a tearing of sections of the platelet matting away from a surface, revealing an area that again can be covered.     

A fourier transform infrared and nuclear magnetic resonance study of cyclized natural rubber

Fourier transform infrared (FTIR), ¹H NMR, and ¹³C NMR have been used to characterize the structure of natural rubber cyclized with p-toluenesulfonic acid. The samples studied were only partially cyclized. The cyclized portions contained both mobile and rigid domains. Crosslinking occurred during the cyclization reaction. The cyclized samples showed a distribution of functionalities including some oxidation products. All three types of olefinic segmented end groups were formed during cyclization (di-, tri-, and tetrasubstituted olefins). The loss of the exocyclic species leads to the formation of cross-linked networks.     

Fourier transform infrared spectroscopy studies of alginate-PLL capsules with varying compositions

Microencapsulation of cells is a promising approach to prevention of rejection in the absence of immunosuppression. Clinical application, however, is hampered by insufficient insight into the factors that influence the biocompatibility of the capsules. Capsules prepared of alginates with a high guluronic (G) acid content proved to be more adequate for clinical application since they are more stable, but, unfortunately, they are less biocompatible than capsules prepared of intermediate-G alginate. In order to get some insight into the physicochemical factors that influence the biocompatibility of capsules for the encapsulation of living cells, the chemical compositions of alginate[bond]Ca beads and alginate[bond]PLL capsules were studied by Fourier transform infrared spectroscopy. We found that during the transition of the alginate[bond]Ca beads to alginate[bond]PLL capsules, Ca connecting the alginate molecules, disappeared at the surface of both high-G and intermediate-G alginate[bond]PLL capsules. At the same time, it turned out that high-G alginate[bond]PLL capsules contained more hydrogen bonding than did intermediate[bond]G alginate capsules. Thus the well-known higher stability of high-G alginate[bond]PLL compared to intermediate-G alginate[bond]PLL capsules is not caused by a higher degree of binding to Ca of the alginate molecules but rather by the presence of more hydrogen bonds. Another observation was that after the transition from bead to capsule, high-G alginate[bond]PLL capsules contained 20% more PLL than the intermediate-G alginate[bond]PLL capsules. Finally, we show that in both high-G and intermediate-G alginate[bond]PLL capsules, the PLL exists in the alpha-helix, in the antiparallel beta-sheet, and in the random coil conformation. This study shows that FT-IR allows for successful analyses of the chemical factors essential for understanding differences in the biocompatibility of alginate[bond]PLL capsules.     

Fourier transform infrared imaging spectroscopy analysis of collagenase-induced cartilage degradation

Collagenase treatment of cartilage serves as an in vitro model of the pathological collagen degradation that occurs in the disease osteoarthritis (OA). Fourier transform infrared imaging spectroscopic (FT-IRIS) analysis of collagenase-treated cartilage is performed to elucidate the molecular origin of the spectral changes previously found at the articular surface of human OA cartilage. Bovine cartilage explants are treated with 0.1% collagenase for 0, 15, or 30 min. In situ collagen cleavage is assessed using immunofluorescent staining with an antibody specific for broken type II collagen. The FT-IRIS analysis of the control and treated specimens mirrors the differences previously found between normal and OA cartilage using an infrared fiber optic probe (IFOP). With collagenase treatment, the amide II/1338 cm(-1) area ratio increases while the 1238 cm(-1)/1227 cm(-1) peak ratio decreases. In addition, polarized FT-IRIS demonstrates a more random orientation of the collagen fibrils that correlate spatially with the immunofluorescent-determined regions of broken type II collagen. We can therefore conclude that the spectral changes observed in the collagenase-treated cartilage, and similarly in OA cartilage, arise from changes in collagen structure. These findings support the use of mid-infrared spectral analysis, in particular the minimally invasive IFOP, as potential techniques for the diagnosis and management of degenerative joint diseases such as osteoarthritis.     

Fourier transform infrared spectroscopy of the polymorphic forms of syndiotactic polystyrene

Infrared spectra of syndiotactic polystyrene exhibiting various crystalline forms and modifications, and in the amorphous state, are reported in this contribution. In addition to strong conformational effects, the spectra demonstrate striking effects of chain packing. Several infrared spectral differences also exist between the two crystalline forms which present a trans-planer conformation of the chains. Spectral changes are also reported for solution-crystallized samples, which depend on the solvent present in the clathrate compound formed with the polymers.     

Fourier transform infrared spectroscopy of follicular fluids from large and small antral follicles

Fourier transform infrared spectroscopy (FTIR) was used to obtain 'biochemical fingerprints' for the constitution of follicular fluids from large and small antral luteinized follicles (n = 54 pairs). All samples gave reproducible characteristic biological infrared absorption spectra, with recognizable amide I protein vibrations and acyl vibrations from fatty acids. Discriminant function analysis of the first derivative FTIR spectra, together with hierarchical cluster analysis used to construct a dendrogram, showed fluid from large follicles formed a homogeneous closely related cluster, whilst that from small follicles was distinct from the large, and heterogeneous in nature. The large follicle fluids showed closer biochemical similarity to each other than to the corresponding fluid taken from small matched follicles. An artificial neural network was trained and following validation with an independent test set, successfully distinguished follicular fluids from large and small follicles. The sex steroid concentrations in the fluids from large and small follicles were significantly different. These results show that fluid from large follicles is distinct in biochemical nature from that from small follicles, but the degree of homogeneity implies size-specific changes take place. These may have consequences for the developmental potential of the oocyte.     

Epitaxy of helical polyolefins: Polymer blends and polymer-nucleating agent systems

Helical polyolefins (polypropylene (PP) and poly(1-butene)) (PB-1) possess crystallographic faces in which the side-groups form well aligned rows. These structural features are shown, through a number of examples, to interact with linear polymers (polyethylene (PE) and polyamides) and nucleating agents. These interactions explain, on the basis of characteristic epitaxial relationships, the mutual activity of certain pairs of crystalline polymers and the hitherto puzzling “universality” of some nucleating agents towards both linear (i.e. PE-like) polymers and helical polyolefins.     

Simultaneous infections with different serogroups of Legionella pneumophila investigated by routine methods and Fourier transform infrared spectroscopy

Simultaneous infections with different Legionella spp. have rarely been described in the literature. We now report on seven sporadic cases of legionellosis of which three were simultaneous infections caused by multiple Legionella pneumophila serogroups. Four different legionellae were involved. L. pneumophila serogroup 1, two different types of L. pneumophila serogroup 4, and L. pneumophila serogroup 10 have been identified simultaneously from a lung tissue specimen of one patient. Specimens from two other patients each revealed two different legionellae of serogroups 1 and 4. The existence of different L. pneumophila serogroups in simultaneous infections has not only been documented by identifying the incriminated Legionella spp. by classical methods. In addition, preliminary results of Legionella spp. identification with the novel physical procedure of Fourier transform infrared spectroscopy have been presented to evaluate its possible applicability for routine diagnostic procedures.     

A new concept to measure cell proliferation using Fourier transform infrared spectroscopy

In our laboratory, we recently developed a new technique to measure cell proliferation that is based on infrared spectro-photometry and the density of cell culture medium. The fluid exchange between intra and extra cellular environments is the key to our method. Using this technique, we found that cell proliferation assessment may be performed much faster than presently existing methods, using two separate pieces of equipment (a cell culture incubator and an interferometer). We confirmed the viability of our method using five different cell lines, breast cancer cells (BT20), mouse normal embryonic fibroblast (NEF) as well as those expressing E6/E7 onco-proteins of human papillomavirus (HPV) type 16, and a human cervical cancer cell line (HeLa). Based on our findings, we propose the design of a mini-incubator allowing cell culture as well as infrared spectra collection of the culture medium, as an accessory to the FTIR work bench, which would become a promising arrangement for continuous cell proliferation monitoring. Moreover, the use of the collected culture medium will be highly efficient in terms of reducing both experimental time and cost.     

Chemometric evaluation of physicochemical properties of carbonated-apatitic preparations by Fourier transform infrared spectroscopy

The purpose of this study was to develop a simple and quick method of evaluating the physicochemical properties of carbonated apatite preparations (CAP) as an index of the bioaffinity of implantable materials based on Fourier-transformed-infrared (IR) spectra by chemometrics. The wet-synthesized CAPs contained various levels of carbonate content (CO(3)), and were analyzed microstrain parameter (MS), crystallite size parameter (CP), specific surface area (Sw), CO(3), and solubility parameter (pK(HAP)) using by X-ray powder diffraction, nitrogen gas adsorption, IR, and UV absorption. The IR spectral results of CAPs suggested that the peak intensities of CAP reflected the physicochemical properties of the samples. The IR data sets were calculated to obtain calibration models evaluating the physicochemical properties of CAPs by a partial least squares regression analysis (PLS). As validation of the calibration model, physicochemical properties of CAP could be evaluated based on validation IR data sets of independent samples, and those values had sufficient accuracy. The regression vector of each calibration model suggested that the physicochemical properties of CAP, such as CO(3), Sw, MS, CP, and pK(HAP), were affected by phosphate, hydroxyl, and carbonate groups.     

Rheo-optical fourier-transform infrared spectroscopy of polymers, 15. Orientational and modificational changes during uniaxial elongation of high-, low- and linear low-density polyethylenes

The transient structural changes of high-, low- and linear low-density polyethylenes were studied by simultaneous mechanical and Fourier-transform infrared (FTIR) spectroscopic measurements. The rheo-optical FTIR data provide a detailed picture of the progress and extent of crystal-axis orientation and orthorhombic-to-monoclinic phase transition during elongation up to 400% strain. Apart from a higher degree of orientation as a consequence of the mechanical treatment, high-density polyethylene may be differentiated from the low-density types by running through a maximum in the content of monoclinic phase upon neck formation. With reference to the investigated structural changes, the linear low-density polyethylenes generally exhibit a behaviour intermediate to the high-density and low-density types.     

Characteristics of crosslinked blends of Pellethene and multiblock polyurethanes containing phospholipid

A series of segmented multiblock polyurethanes (MPUs) were synthesized by polyaddition reaction using hexamethylene diisocyanate (HDI)/poly(ethylene oxide) (PEO, as a hydrophilic component)/ poly(tetramethylene oxide) (PTMO)/ poly(butadiene diol)(PBD)/1,4-butanediol(BD)/(2-[bis(2-hydroxyethyl) methyl ammonio]ethyl stearyl phosphate)[BESP, as a phospholipids component: 0-42 mol% (0-9 wt%)]. To improve the blood compatibility of biomedical grade polyurethane (Pellethene), the Pellethene was blended with MPUs and then crosslinked using dicumyl peroxide as a crosslinking agent. Effects of BESP content [0-42 mol% (0-9 wt%)] in MPUs on the properties of MPUs and blend (Pellethene/MPUs) films were investigated. The X-ray photoelectron spectra indicated that the BESP moieties were located at the surface of the crosslinked blend (Pellethene/MPUs) films. As the BESP content in MPUs increased, the water contact angle on the surfaces of crosslinked blend film was decreased but the water absorption and mechanical properties were markedly increased. By the test of platelet adhesion on the surfaces of crosslinked blend film, it was found that the platelet adhesion on the surface was significantly decreased from 70% to 6% by increasing BESP content from 0 to 42 mol% (0-9 wt%) in MPUs. These results suggest that crosslinked blend films may have more potential as a new material for biomedical applications, which are directly in contact with blood.     

Implementation of Fourier transform infrared spectroscopy for the rapid typing of uropathogenic Escherichia coli

In this paper, we demonstrate that Fourier transform infrared (FT-IR) spectroscopy is able to discriminate rapidly between uropathogenic Escherichia coli (UPEC) of key lineages with only relatively simple sample preparation. A total of 95 bacteria from six different epidemiologically important multilocus sequence types (ST10, ST69, ST95, ST73, ST127 and ST131) were used in this project and principal component-discriminant function analysis (PC-DFA) of these samples produced clear separate clustering of isolates, based on the ST. Analysis of data using partial least squares-discriminant analysis (PLS-DA), incorporating cross-validation, indicated a high prediction accuracy of 91.19 % for ST131. These results suggest that FT-IR spectroscopy could be a useful method for the rapid identification of members of important UPEC STs.     

A study of the nature and formation of zinc polyacrylate cement using Fourier transform infrared spectroscopy

The formation and structure of zinc polyacrylate has been studied by Fourier transform infrared spectroscopy (FTIR). Using this technique we have shown that the fully hardened cement is bonded predominantly by zinc carboxylate complexes, rather than by associations of purely ionic character as had previously been supposed. Ionic bonds are formed in the initial stages of the reaction but are gradually converted to complex forms. This bond rearrangement appears partly responsible for physical changes that occur during gelation, setting, and hardening.     

Spectroscopic quantitative analysis of blood glucose by Fourier transform infrared spectroscopy with an attenuated total reflection prism.

As an alternative way of long-term glycemic monitoring, the glucose measurement by analyzing Fourier transform infrared absorbance spectra with an attenuated total reflection prism has been developed. In glucose aqueous solution, glucose has characteristic absorptions at the wave numbers of 1033 and 1080 cm-1 and the absorption intensities are proportional to glucose concentrations. In serum and whole blood samples, however, red blood cell corpuscles, serum albumin and serum gamma-globulin interfere with the absorbance spectra of glucose and shift the base line upward significantly. Therefore, to eliminate these interferences in serum and whole blood samples, the feasibility of the calibration curves obtained by using difference absorbance spectra with those of fasting samples was studied. As a result, highly significant correlations between glucose concentrations estimated by Fourier transform infrared spectroscopic method and those measured by glucose oxidase method were obtained (r = 0.981 and 0.989 for serum and whole blood samples, respectively). From these experiments, it was concluded that by infrared spectroscopy glucose concentrations in the serum and whole blood samples could be measured quantitatively or monitored if the base line drifts and interferences were subtracted.     

Reactive compatibilization of HDPE/PET blends by glycidyl methacrylate functionalized polyolefins

Blends of high-density polyethylene (HDPE) and poly(ethylene terephthalate) (PET) in weight compositions of 20/80, 40/60, 60/40 and 80/20 were modified with glycidyl methacrylate functionalized polyolefins with the aim of improving the compatibility and in particular elongation and impact strength. The compatibilizers used were ethylene/glycidyl methacrylate copolymers (E/GMA) and ethylene/ethyl acrylate/glycidyl methacrylate terpolymers (E/EA/GMA) with variable contents of reactive functions (1 to 8 wt.-% of glycidyl methacrylate). The effects of the compatibilizers were evaluated by studying the mechanical properties and the morphology of the blends. The addition of 5 wt.-% of functionalized polyolefins was found sufficient to improve ductility and impact strength of all compositions. A more pronounced compatibilizing effect was obtained with the functionalized terpolymer containing the smallest amount of glycidyl methacrylate. With this emulsifying agent, elongation at break is increased by a factor of four for the compositions near the inversion of phases. However, the main interest of this work is that it provides a compatibilization of immiscible blends of polyolefin and polyester by injection moulding. This melt processing is very interesting from an industrial point of view because it proves that materials with good mechanical properties can be obtained in one step of processing.