Crystallization behavior of poly(3,3-bisethoxymethyl oxetane) and poly(3,3-bisazidomethyl oxetane)

Two crystal modifications have been found for poly(3,3-bisethoxymethyl oxetane) [poly- (BEMO)] by wide-angle x-ray powder diffraction and differential scanning calorimetry, while only one modification has been found for poly(3,3-bisazidomethyl oxetane) [poly(BAMO)]. Melting temperatures for the two polymers were nearly the same, varying from about 70 to about 90°C depending on the thermal treatment; higher crystallization temperatures resulted in higher melting temperatures. The equilibrium melting temperature T was found to be 125 and 128°C for poly(BEMO) and poly(BAMO), respectively, by using the Hoffman-Weeks extrapolation procedure. Measurement of the melting-point depression of Poly(BEMO) and poly(BAMO) in dibutyl phthalate yielded enthalpy of fusion values of 2.25 and 12.8 kcal/mol, respectively. The percent crystallinity for poly(BEMO) and poly(BAMO), respectively, was calculated to be 55-60 and 13-30% based on DSC and x-ray analysis.     

Crystallization kinetics of poly(3,3-diethyl oxetane)

Poly(3,3-diethyl oxetane) fractions (number-average molecular weights from 10,000 to 800,000) have been isothermally crystallized from the relaxed melt state in the temperature range 10–65°C; two crystalline modifications are formed, orthorhombic in the range 10–25°C and monoclonic in the range 45–65°C. The influences of molecular weight and undercooling on the crystallization kinetics have been analyzed. The crystallization temperature-coefficient was determined; a variation of the product of the interfacial energies was found in the range of molecular weights which has been examined. Comparison of the experimental results for this polymer with those reported for other polyoxetanes shows that the crystallization rate for a given undercooling is lower for PDEO than for PDMO and PTO and that the interfacial basal free energies decrease from polyoxetane to the 3,3-dialkyl oxetanes.     

Crystallization kinetics of the monoclinic modification of poly(3,3-dimethyl oxetane)

Poly(3,3-dimethyl oxetane) fractions ranging in number average molecular weights from 18500 to 130000 have been isothermally crystallized from the relaxed melt state in the temperature range from 12 to 44 °C, where only the monoclinic modification is formed. The influence of molecular weight and undercooling in crystallization kinetics has been analyzed. The level of crystallinity is very slightly dependent on molecular weight but the influence of this parameter on the time scale of the crystallization is relatively pronounced. The crystallization temperature coefficient was determined and it was found a constant value of the product of the interfacial energies in the range of molecular weights which has been analyzed. Growth rate measurements were carried out for fraction ¯M _n=130000 and it was found that the temperature coefficients for overall and growth rates are equal. Finally, the comparison of the experimental results for this polymer with those reported for poly(oxetane) shows two main differences: first, the crystallization rate is slower for poly(3,3-dimethyl oxetane) and second, the temperature coefficient is smaller for this polymer.     

Thermoelastic and dielectric studies of poly(3,3-dimethyl oxetane) chains

Poly(3,3-dimethyl oxetane) was synthesized by ring opening polymerization of 3,3-dimethyl oxetane. Elongation experiments were performed on unswollen elastomeric networks prepared from this polymer over the temperature range 30–90°C. The changes in the tensile stress while the networks crystallized were examined at various elongations. From thermoelastic data which were free from the effects of network crystallization, the temperature coefficient of the chain dimensions was found to be 1.1 × 10^?3 K^?1 in the vicinity of 60°C. The dipole moment ratio and its temperature coefficient were also measured; the average values of these parameters at 30°C were 0.20₆ and 2.5 × 10^?3 K^?1, respectively. All of these experimental-configuration-dependent properties were critically interpreted in terms of the rotational isomeric-state model. In comparing theory and experiment, conclusions were obtained which confirm earlier results according to which gauche states about C—C skeletal bonds in poly(3,3-dimethyl oxetane) are strongly favored over the alternative trans states.     

Raman spectroscopy studies on structural modifications in poly(3,3-dimethyl oxetane)

Monoclinic(II) and orthorhombic(III) modifications of poly(3,3-dimethyl oxetane) can be obtained from the relaxed melt state depending on crystallization temperature. However, if the crystallization of a given modification is not completed, the other modification can be obtained from the amorphous phase. Raman spectroscopy has been used to study the influence of the temperatures and times of crystallization on the structural modifications of this polymer. The influence of the annealing process on the crystalline amount is also examined.     

Crystallization and melting behaviour of poly(ferrocenylsilanes)

A series of poly(ferrocenyldimethylsilanes) was prepared anionically in order to study their melting behaviour. The DSC traces of these polymers displayed multiple endotherms that could be assigned to melting of lamellae with varying thicknesses. Upon heating, thinner lamellae are converted into thicker ones in a continuous melting-recrystallization process.     

Crystallization and melting behaviour of poly(m-xylene adipamide)

The melting and crystallisation behaviour of poly(m-xylene adipamide) (MXD6) are investigated by using the conventional DSC, X-ray diffraction and polarised light microscopy. Triple, double or single melting endotherms are obtained in subsequent heating scan for the samples after isothermal crystallisation from the melt state at different temperatures. The lowest melting peak can be ascribed to the melting of secondary crystals. The melting of primary crystals causes the medium melting peak and the highest melting peak is attributed to the melting of recrystallised species formed during heating. Following the Hoffman–Weeks theory, the equilibrium melting temperature is equal to 250°C and the equilibrium melting enthalpy ΔH _m ⁰ to 175 J g^–1. Then, using the Lauritzen–Hoffmann theory of secondary crystallisation, the analyse of the spherulitic growth shows that the temperature of transition between the growing regimes II and III is equal to 176°C. Finally the Gibbs-Thomson relationship allows the determination of the distribution function of crystalline lamellae.     

Effect of molecular weight on crystallization and rheological properties of poly(3,3-bis(azidomethyl)oxetane)

Various molecular weight of poly(3,3-bis(azidomethyl)oxetane) were prepared from 3,3-bis(chloromethyl) oxetane. The structure of those were confirmed by Fourier transform infrared, proton nuclear magnetic resonance spectral analysis and gel permeation chromatograph, meanwhile the properties were also compared by X-ray diffraction, differential scanning calorimetry and rheological analysis. The results indicated that increasing molecular weight weakened the crystallization ability of PBAMO and increased the glass transition temperature. Furthermore, the viscosity, shear stress, G′ and G″ of PBAMO increased gradually with increasing of the molecular weight.     

Influence of the crystallinity on the Raman spectra of poly(3,3- dipropyl oxetane)

Raman spectra of semicrystalline Poly(3,3-dipropyl oxetane) is observed clearly influenced by the crystal/amorphous ratio, on the same way to the other elements of the branched polyoxetanes series. The compound is submitted to different annealing processes and the evolution of the amorphous and crystal band intensities is analysed and compared with the results obtained by calorimetric measurements.     

Surface characterization of biocidal polyurethane modifiers having poly(3,3-substituted)oxetane soft blocks with alkylammonium side chains

This paper focuses on surface characterization of P[ AB] copolyoxetane soft block polyurethanes having either fluorous (3FOx, -CH2OCH 2CF3) or PEG-like (ME2Ox, -CH2(OCH2CH2) 2OCH3), A side chains and alkylammonium, B side chains. Physical surface characterization data were analyzed in light of the previously observed order of antimicrobial effectiveness for a set of four surface modifiers. Ample physical evidence for surface concentration of fluorous 2 wt % P[ AB]-polyurethane modifiers was obtained from XPS, contact angles, ATR-IR spectroscopy, and TM-AFM. In TM-AFM phase imaging, the most effective biocidal surface modifier, 2 wt % HMDI-BD(30)/P[(3FOx)(C12)-0.89:0.11]-PU, showed a nanoscale phase-separated structure consisting of 200 nm domains with background features about 10 times smaller. Despite similar surface characterization data, the 2 wt % fluorous C6 analog ranked third in contact biocidal effectiveness. Physical evidence for surface concentration of 2 wt % P[(ME2Ox)(C12)-0.86:0.14]-PU was modest, considering that antimicrobial effectiveness was second only to 2 wt % HMDI-BD(30)/P[(3FOx)(C12)-0.89:0.11]-PU. In this set of surface modifiers, nanoscale morphology is largely driven by the fluorous component, whereas antimicrobial effectiveness is more strongly influenced by alkylammonium chain length. The effect of alkylammonium side chain length on surface concentration and antimicrobial behavior is more pronounced for ME2Ox polyurethanes compared to the 3FOx analogs.     

Cationic copolymerization of 3,3-bis(chloromethyl) oxetane with vinyl compounds

Copolymerizations of 3,3-bis(chloromethyl)oxetane (BCMO) with some vinyl compounds were carried out with cationic catalysts in various solvents to determine what kind of vinyl compound is able to copolymerize with BCMO. p-Methylstyrene (pMS), 2-chloroethyl vinyl ether (CEVE), α-methylstyrene (αMS), and isobutene (IB) were used as comonomers. The rate of consumption of each monomer was measured by gas chromatrography. Plots of copolymer composition in the copolymerization of BCMO with pMS were characterized by S-shaped curves in several solvents. As poly-BCMO is insoluble and the vinyl polymers are soluble in benzene, the polymers obtained were separated into benzene-soluble and benzene-insoluble fractions, and the composition of each fraction was determined by elemental analysis. It was found that pMS, CEVE and IB formed a copolymer with BCMO, but αMS produced no copolymer with BCMO. Thus the formation of copolymer between a cyclic ether and some vinyl monomers was observed by a cationic mechanism. The cross-propagation mechanism is discussed on the basis of these results.     

Crystallization of poly(ethylene oxide) fractions: Crystallization isotherms

The crystallization kinetics of a range of fractions of poly(ethylene oxide) are presented and analyzed. It is concluded that deviations from the Avrami equation with exponent of 3 are mainly due to rejection of low molecular weight molecules for the low molecular weight fractions (M?_n < 6,000) and to a process of crystal perfecting for the high molecular weight fractions (M?_n > 6,000).     

Structural changes in poyl(3,3 dimethyl oxetane) studied by Raman spectroscopy

The influence of the applied stress and stretch on Poly(3,3 dimethyl oxetane), thermically crystallized, has been studied using Raman spectroscopy. The effect of these mechanical deformations produces a transformation from the orthorhombic to monoclinic structure which is the thermodynamically most stable form.     

Synthesis of 3,3-disubstituted oxetane building blocks

The synthesis of two different sets of 3,3-disubstituted oxetane building blocks is described. These molecules can be usefully incorporated in more complex structures to modulate their metabolic and physicochemical properties. The synthetic pathways are general and could be exploited for the synthesis of many other related derivatives.     

Flammability and thermal behaviour of phosphorus-containing polyamides. Copolymers of poly(1,4-phenylene terephthalamide), poly(1,3-phenylene isophthalamide), poly(1,4-phenylene sebacylamide) and poly(1,3-phenylene sebacylamide)

Some flame retardant copolyamides derived from 1,4-phenylenediamine or 1,3-phenylenediamine and N,N′-bis[(dialkoxyphosphinyl)methyl]1,4-benzenediamine with terephthaloyl or isophthaloyl, or sebacoyl dichlorides, are reported. Thermal and thermo-oxidative stability were studied by means of TGA. The influence of chemical structure in enhancing thermo-oxidative resistance of copolyamides was established. In the case of sebacylamides the DSC thermograms were also obtained. The flammabilities of the copolymers were determined by means of the limiting oxygen index; in the case of sebacylamides, the limiting nitrous oxide index was also determined. Comparison of LN₂OI with the LOI in sebacylamides reveals that the action of the flame retardant groups affects mainly the condensed phase decomposition. This view is also supported from the new stage of decomposition revealed in the DTGA thermograms.     

Electron spin resonance study of irradiated monomer and polymer of 3,3-bis(chloromethyl)oxetane

ESR spectra were studied for irradiated 3,3-bis(chloromethyl)oxetane (BCMO) single crystals and poly-BCMO obtained by polymerizing BCMO single crystals in solid state. In both cases, the spectra consist of the superposition of two-line and threeline components at ?196°C. On warming the sample, only the former survived. From the examination of hyperfine coupling tensors, it is concluded that the two-line spectrum is due to the free radicals for the monomer and ? C(CH₂Cl)₂? ?H? O? for the polymer sample, respectively. The orientation of the free radicals gives information about the mode of ring opening in the solid-state polymerization of BCMO.