Heat capacity and phonon dispersion in poly(L-methionine)

Poly(L -methionine) (PMet) is one of the two sulfur containing polyamino acids. Raman, FTIR spectra, and heat capacity measurements of PMet have been well interpreted through the normal mode analysis and the density of states derived therefrom. Earlier interpretation of heat capacity data is limited because it is based on the Tarasov model, wherein the concept of group frequency and skeletal similarity are used. A special feature of some dispersion curves is their tendency to bunch in the neighborhood of the helix angle. This has been attributed to the presence of strong intramolecular interactions. Repulsion between the dispersion curves is also observed. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 2281–2292, 1997     

Evaluation by Fourier Transform Infrared Spectroscopy of the different crystalline forms in syndiotactic polystyrene samples

Fourier transform infrared (FTIR) spectra of syndiotactic polystyrene (s-PS) semicrystalline samples have been examined by using the spectral subtraction approach. For the crystalline forms including trans-planar chains (trigonal α and orthorhombic β) a number of conformational and structural order effects, not previously described in the literature, have been identified. A method based on the results of the spectral subtraction analysis has been developed for the determination of the crystallinity degree and compared with the standard method based on the wide-angle X-ray diffraction patterns. The spectral subtraction analysis on FTIR spectra allows also an easy evaluation of the amount of α and β crystalline phases (often simultaneously present in melt-crystallized samples) although both contain chains in a same conformation. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 1055–1066, 1997     

Interaction of metal ions with polypyrrole on polyacrylic acid matrix

The oxidative matrix polymerization of pyrrole (Py) by Fe(III), Cu(II), Ni(II), Co(II), and Zn(II) in the presence of polyacrylic acid (PAA) was studied and water‐soluble products along with insoluble products were obtained. The metal (Me) content of the insoluble part was determined by using atomic absorption spectroscopy (AAS). The effects of the oxidation potential of Me ions and ligands on the aggregation of polypyrrole (PPy) on the matrix polymer were measured by ultraviolet (UV)‐visible spectra. These findings also were checked by cyclic voltammetry (CV) measurements on PAA–Cu and PAA–PPy–Cu interactions. The conductometric titration results of PAA–PPy–Me ternary solutions were explained in the light of the interaction of Me ions with Py to polymerize on the PAA matrix resulting in some free carboxyl groups with a possibility of having Me–polymer complexes and a ternary complex (PAA–Me–PPy). The insoluble products were characterized by Fourier transform infrared (FTIR), elemental analysis, scanning electron microscopy (SEM), and four point probe conductivity measurements. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1115–1123, 1999     

Effect of X-ray radiation on the structure of P (VDF/TrFE) copolymers

Structural changes in poly(vinylidene fluoride)-trifluoroethylene [P(VDF-TrFE)] copolymers caused by X-ray irradiation were investigated by molecular weight determination, EPR analysis, FTIR spectroscopy, gel content, DSC thermal analysis, X-ray diffraction, and piezoelectricity measurements. Samples exhibit radiation-induced conductivity (RIC) due to the formation of radical ions. These radicals are generated by bond cleavage, which could react, leading to structural changes such as oxidation, double bond formation, chain scission, and crosslinking. The increasing gel content with radiation dose indicated that crosslinkings of the polymer chains predominate. Irradiation on P(VDF-TrFE) caused the melting temperature, heat of fusion, and Curie temperature to decrease. These results are consistent with the partial destruction of crystalline domains. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 1201–1205, 1997     

Blend of electroactive poly(3-dodecylthiophene) with comb-like alkylated polyacrylate

The conformational mode change of the stiff alkylated polymer, poly(3-dodecyl thiophene) (PDDT), with a flexible comb-like coil poly(octadecyl acrylate) (PODA), and the effect of intermolecular interaction between these two alkylated polymers with different chemical structure of the backbone were investigated using UV-Vis spectroscopy, Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimeter (DSC), and wide-angle x-ray diffraction (WAXD). In addition to the characteristics of thermochromism, a homogeneous one phase was observed above 175°C when the PODA content was 10 wt % or less. Increased conductivity in the PDDT/PODA blend due to the highly conjugated π-system of PDDT backbone was observed in the presence of nonelectroactive PODA. A red-shift of absorption maximum of PDDT/PODA blend observed in solid state at room temperature. From the FTIR spectra, the gauche-trans conformational structure change of methylene units was investigated in two alkylated polymer blends. The increase of combined heat of fusion of the alkyl side chain melting of PDDT and the endothermic peak of PODA, as well as the interlayer d-spacing of PDDT main chain were also observed with the addition of PODA in blends. A more ordered conformational structure of rigid rod backbone of PDDT was induced due to the attractive intermolecular interaction which can cause cocrystallization between the alkylated side chains of two polymers. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 :1025–1041, 1997     

Polybisaminophosphazene-silver nitrate complexes: Coordination and properties

Poly[bis(propylamino)phosphazene]-silver nitrate complexes and poly[bis-(butylamino)phosphazene]-silver nitrate complexes with various salt contents, which are new polyphosphazene-salt complexes, have been prepared. The complexes were characterized by FTIR, ³¹P-NMR, and ¹³C-NMR spectroscopies, and the thermal properties were studied by DSC, TGA, and TGA/FTIR measurements. It was found that the poly[(bisamino)phosphazene]-silver coordination may occur both at the backbone nitrogen and the side chain nitrogen and incorporation of silver nitrate into the polymer lowered the decomposition temperature. The complexes can be cast as freestanding film with good dimensional stability. Compared to their parent polymers, the highest conductivities of the films are increased three to four orders in magnitude at room temperature. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1023–1031, 1997     

Diffusion of methyl ethyl ketone in polyisobutylene: Comparison of spectroscopic and gravimetric techniques

In this study, vapor sorption FTIR–ATR (Fourier Transform Infrared Attenuated Total Reflectance) spectroscopy was combined with a conventional gravimetric sorption balance to examine diffusion in polymers. Mutual diffusion coefficients of methyl ethyl ketone in polyisobutylene were measured using both methods at various penetrant activities and temperatures in the range 40–60°C. Actual penetrant concentrations were determined from the sorption balance. The diffusion coefficients from the two techniques agree very well with each other. In addition, the diffusivity data from both techniques could be correlated successfully as a function of temperature and concentration with the Vrentas and Duda free-volume model. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 1261–1267, 1997     

Structure and molecular conformation of tussah silk fibroin films: Effect of heat treatment

Structural changes of tussah (Antheraea pernyi) silk fibroin films induced by heat treatment were studied as a function of the treatment temperature in the range 200–250°C. The DSC curve of tussah films with α-helix molecular conformation displayed characteristic endo and exo peaks at 216 and 226°C, respectively. These peaks first weakened and then completely disappeared after heating at 230°C. Accordingly, the TMA thermal shrinkage at 206°C disappeared when the films were heated at 230°C. The onset of weight loss was monitored at 210°C by means of TG measurements. X-ray diffraction profiles gradually changed from α-helix to β-sheet crystalline structure as the treatment temperature increased from 200 to 250°C. On raising the heating temperature above 200°C, the intensity of IR and Raman bands characteristic of β-sheet conformation increased in the whole ranges of amide and skeletal modes. The sample treated at 200°C showed a spectral pattern intermediate between α-helix and β-sheet molecular conformation. The IR marker band for random coil structure, still detectable at 200°C, disappeared at higher treatment temperatures. Spectral changes attributable to the onset of thermal degradation appeared at 230°C. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 841–847, 1997     

Chemical synthesis and characterization of poly(aniline‐co‐ethyl 3‐aminobenzoate) copolymers

Copolymers of aniline and ethyl 3‐aminobenzoate (3EAB) were synthesized by chemical polymerization in several mole ratios of aniline to functionalized aniline, and their physicochemical properties were compared to those of poly(aniline‐co‐3‐aminobenzoic acid) (3ABAPANI) copolymers. The copolymers were characterized with UV–vis, FTIR, Raman, SEM, EPR, and solid‐state NMR spectroscopy, elemental analysis, and conductivity measurements. The influence of the carboxylic acid and ester group ring substituents on the copolymers was investigated. The spectroscopic studies confirmed incorporation of 3ABA or 3EAB units in the copolymers and hence the presence of C?O group in the copolymer chains. The conductivity and EPR signals both decreased with increasing 3EAB content of the copolymers emeraldine salt (ES) form. The conductivity of the ES form of 3ABAPANI was found to be high (1.4 × 10^?1 S cm^?1) compared with the conductivity (10^?2–10^?3 S cm^?1) of 3EABPANI (ES) copolymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1339–1347, 2010     

Conformational transition of polyelectrolytes in mixed solvent by dielectric spectroscopy: Electrostatic and hydrophobic interactions

We studied conformational transition of poly(acrylic acid)‐graft‐dodecyl (PAA‐g‐dodecyl), and PAA‐graft‐poly(ethylene oxide)‐graft‐dodecyl (PAA‐g‐PEO‐g‐dodecyl) molecules in DMF/H₂O solvent by dielectric analysis method utilizing a double‐layer polarization theory. In addition to the hydrophobic interaction which has been demonstrated to be vital for their conformational transition with water content, it is confirmed that the electrostatic interaction is crucial. For PAA‐g‐dodecyl molecules, at a critical value of water content, a peak value of correlation length is reached originating from the delicate balance between electrostatic and hydrophobic interactions. For PAA‐g‐PEO‐g‐dodecyl molecules, chains conformation is mainly determined by electrostatic interaction over the entire range of water content due to the low content of dodecyl groups. Meanwhile, H‐bond associative interaction prevents the dissociation of free carboxyl groups over the range of lower water content, thus their stretched transition moves to higher water content. Our results provide the underlying insights needed to understand solvent effect on the conformational transition for polyelectrolytes with hydrophobic groups. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1716–1724     

Ethylene polymerization and copolymerization with a polar monomer using an α‐iminocarboxamide nickel complex activated by trimethylaluminum

An α‐iminocarboxamide nickel complex was activated by trimethylaluminum (TMA) and used in the polymerization of ethylene and its copolymerization with 10‐undecen‐1‐ol. The best activity was observed upon activation with 9 equiv of TMA at a temperature of 26 °C. NMR spectroscopic studies did not show 10‐undecen‐1‐ol incorporation. However, FTIR analyses suggest the incorporation of a very small amount of comonomer, which affects the glass transition temperature, the degree of branching, and the mechanical properties of the materials. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 54–59, 2008     

In situ FTIR spectroscopic study of the recently detected low‐temperature‐induced structural changes in isotactic polypropylene

The in situ Fourier transform infrared spectroscopic study of isotactic polypropylene showed that structural changes are induced at liquid nitrogen temperature, and start to show up in the FTIR spectra with heating from ?196 to +200 °C. This structural change leads to the detection of an abnormal behavior in the MIR absorption spectra of the investigated sample. Lowering the temperature brought the chains closer together and so increased the interchain interaction. At ?196 °C splitting of some regularity bands assigned to helical chains within the crystalline region was observed, showing that the regularity of the chains increases because of cooling. Heating the samples from liquid nitrogen temperature caused an opposite conformational disordering, which resulted in the appearance of several new broad bands in the ranges: 600–700, 1614–1640, and 3050–3550 cm^?1. These structural changes might be due to both twisting and folding of the chains, which gave rise to bands assigned to the various bending modes of CH₂ molecules, in addition to the rotational isomers (conformers) resulting from rotation of the vinyl and alkyne end groups. Moreover, our experimental study of the behavior of several regularity bands suggests that at temperatures in the vicinity of +120 °C another high temperature structural change resulting from the disordering of helical sequences in the noncrystalline region takes place. Differential scanning calorimetry thermograms of the thermally treated and an untreated sample were found to confirm the obtained results. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2829–2842, 2005     

Photochemical behavior of poly(ethylacryloylacetate) and poly(acryloylacetone) films

Films of poly(ethylacryloylacetate) (PEAA) and poly(acryloylacetone) (PAA) were subjected to UV irradiation (λ = 254 nm) at room temperature. The photoinduced structure transfer from cis-enol onto a diketo forms has been investigated. The structure transfer caused by UV light was found to be slower than for the corresponding process in solution. The spectral investigations (UV, IR) showed reversible process of photoketonization. The results were analyzed in terms of the model for the participation of the trans-enol form in the process of the ketonization. Based on the results obtained, some general conclusions were made about the organization of the units in the polymer chain. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3683–3688, 1997     

FTIR spectroscopic study on crystallization process of poly(ethylene-2,6-naphthalate)

In situ Fourier transform infrared (FTIR) measurements were carried out to elucidate conformation changes occurring during the isothermal melt crystallization of poly(ethylene-2,6-naphthalate) (PEN). Based on the band assignments for the components of the amorphous, α-crystal form, and β-crystal form of PEN in film samples, the in situ data was analyzed in terms of the amorphous- and crystal-trans conformations. It was observed at a higher isothermal crystallization temperature that the formation of amorphous-trans conformations precedes the growth of crystals. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2741–2747, 1997     

Method for grafting poly(acrylic acid) onto nylon 6,6 using amine end groups on nylon surface

Several methods have been developed for grafting materials to the surface of polymers to alter their surface characteristics. This article reports a procedure for grafting poly(acrylic acid) (PAA) onto nylon 6,6 films via the naturally occurring amine end groups of nylon 6,6 using N‐hydroxy‐succinimide in conjunction with 1‐ethyl‐3‐ (3‐dimethylaminopropyl)carbodiimide hydrochloride (EDC) facilitated amidazation. Reaction conditions were investigated with respect to PAA molecular weight, activator concentrations, reaction temperature, and time. X‐ray photoelectron spectroscopy showed that surface coverage of more than 50% was consistently achieved for 250 kD PAA. The maximum grafting occurred at room temperature with a large excess of EDC with a reaction time of 30 min. The same level of grafting can be achieved using smaller amounts of EDC at 60 °C. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 719–728, 2002; DOI 10.1002/pola.10149     

In situ FT‐Raman spectroscopic study of the conformational changes occurring in isotactic polypropylene during its melting and crystallization processes

The conformational changes occurring in isotactic polypropylene during the melting and crystallization processes have been carefully investigated using FT‐Raman spectroscopy at temperatures below, at, and above the polymer melting point. Results confirmed the retention of some crystallinity up to +210 °C, which is 50 °C above the melting point. It was found that, at temperatures just above the melting point (1–10 °C), there is still some short range order of at least 12 monomer units long in certain regions of the melt. At 10 °C above the melting point, the short range order drops below 12 monomer units resulting in the disappearance of the Raman band at 841 cm^–1. Vice versa, the experimental measurements show that the iPP melt system is stable when the persistence length of helical sequences is less than 12 monomer units. As soon as the helix length exceeds 12 units, the 3₁ helix conformation extends quickly and then crystallization occurs. These results are discussed in terms of Imai's microphase separation theory and it agreed very well with it. Also, from our observations for correlation splitting, Raman bands related to conformational states were identified. This analysis indicates the existence of three different conformational states at 808, 830, and 841 cm^–1. The 808 cm^–1 band was assigned to helical chains within crystals (representing crystalline phase). The 841 cm^–1 band was shown to be composed of a band at 841 cm^–1, assigned to shorter chains in helical conformation with isomeric defects (representing the isomeric defect phase), and a broader band at 830 cm^–1 assigned to chains in nonhelical conformation (representing the melt‐like amorphous phase). This indicates the detection of a three‐phase structure in iPP, where a third phase could be due to the presence of defect regions within the crystalline region, or due to the presence of an amorphous–crystal interphase. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2173–2182, 2006     

Linear diacetylene polymers containing bis(dimethylsilyl) phenyl and/or bis-(tetramethyldisiloxane) carborane residues: Their synthesis,characterization and thermal and oxidative properties

A series of inorganic-organic linear diacetylenic hybrid polymers ( 5a–e ) were prepared by the polycondensation reaction of 1,4-dilithiobutadiyne with 1,4-bis(dimethylchlorosilyl)benzene and/or 1,7-bis(tetramethylchlorodisiloxane)-m-carborane. Their structures were characterized using FTIR, and ¹³C and ¹H NMR spectroscopies, and their thermal and oxidative properties were evaluated by DSC and TGA analyses. The hybrid polymers exhibited solubility in common organic solvents and were viscous liquids or low melting solids at room temperature. Broad prominent exotherms, attributed to reaction of the diacetylenic units, were observed by DSC in the 306°C to 354°C temperature range. When 5a–e were analyzed by TGA to 1000°C under nitrogen, weight retention between 79 and 86% were obtained. Ageing studies, performed at elevated temperatures in air on a thermoset and a ceramic obtained from polymer 5b , showed this system to have excellent thermal and oxidative stability. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2387–2391, 1997     

Synthesis,characterization, and electrical properties of polypyrrole/multiwalled carbon nanotube composites

Size‐controllable polypyrrole (PPy)/multiwalled carbon nanotube (MWCNT) composites have been synthesized by in situ chemical oxidation polymerization directed by various concentrations of cationic surfactant cetyltrimethylammonium bromide (CTAB). Raman spectra, FTIR, SEM, and TEM were used to characterize their structure and morphology. These results showed that the composites are core (MWCNT)–shell (PPy) tubular structures with the thickness of the PPy layer in the range of 20–40 nm, depending on the concentration of CTAB. Raman and FTIR spectra of the composites are almost identical to those of PPy alone. The electrical conductivities of these composites are 1–2 orders of magnitude higher than those of PPy without MWCNTs. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6449–6457, 2006     

Synthesis and characterization of poly(dimethylsiloxane‐urethane) elastomers: Effect of hard segments of polyurethane on morphological and mechanical properties

A series of poly(dimethylsiloxane‐urethane) elastomers based on hexamethylenediisocyanate, toluenediisocyanate, or 4,4′‐methylenediphenyldiisocyanate hard segment and polydimethylsiloxane (PDMS) soft segment were synthesized. In this study, a new type of soft‐segmented PDMS crosslinker was synthesized by hydrosilylation reaction of 2‐allyloxyethanol with polyhydromethylsiloxane, using Karstedt's catalyst. The synthesized soft‐segmented crosslinker was characterized by FT‐IR, ¹H, and ¹³C NMR spectroscopic techniques. The mechanical and thermal properties of elastomers were characterized using tensile testing, thermogravimetric analysis, differential scanning calorimetry (DSC), and dynamical mechanical analysis measurements. The molecular structure of poly(dimethylsiloxane‐urethane) membranes was characterized by ATR‐FTIR spectroscopic techniques. Infrared spectra indicated the formation of urethane/urea aggregates and hydrogen bonding between the hard and soft domains. Better mechanical and thermal properties of the elastomers were observed. The restriction of chain mobility has been shown by the formation of hydrogen bonding in the soft and hard segment domains, resulting in the increase in the glass‐transition temperature of soft segments. DSC analysis indicates the phase separation of the hard and soft domains. The storage modulus (E′) of the elastomers was increasing with increase in the number of urethane connections between the hard and soft segments. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2980–2989, 2006