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 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.     

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 behaviour of polyoxetanes: poly(oxetane), poly (3,3-dimethyloxetane) and poly(3,3-diethyloxetane)

The influence of the crystallization temperature on the melting behaviour and crystalline structure of polyoxetane (PTO), poly(3,3-dimethyloxetane) (PDMO) and poly(3,3-diethyloxetane) (PDEO) has been studied using differential scanning calorimetry (DSC) and X-ray techniques. When PTO is crystallized by cooling from the relaxed melt state, only the orthorhombic modification is obtained. However, PDMO and PDEO can be crystallized in two different modifications depending on crystallization temperature. The effect of the substituents in the stability of main chain conformations in crystalline state is discussed.     

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.     

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.     

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.     

Polymerization of 3,3-dimethyl selenetane

3,3-Dimethyl selenetane has been polymerized under the influence of different cationic and anionic catalysts. Cationic polymerization led to limited conversions because of the occurrence of a termination reaction between the growing chains and the formed polymer. The obtained polymers had low molecular weights. Anionic polymerization gave polymers with molecular weight up to 35,000. The mechanisms of polymerization are believed to be analogous to the mechanisms proposed for the polymerization of thietanes.     

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.     

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.     

Tetrahydrofuran and 3,3-bis(chloromethyl) oxetane triblock copolymers synthesized by two-end living cationic polymerization

Triblock copolymers based on tetrahydrofuran (THF) and 3,3-bis(chloromethyl) oxetane (BCMO), BCMO-block-THF-block-BCMO and poly(BCMO-co-THF)-THF-(BCMO-co-THF), have been synthesized by two-end living cationic polymerization with a bifunctional initiator, trifluoromethanesulfonic anhydride [(CF₃SO₂)₂O]. The polymers are obtained by using the two end propagating species of poly(THF) to initiate the sequential BCMO polymerization. The resulting polymers are characterized by infrared (IR), nuclear magnetic resonance (NMR), and differential scanning calorimetry (DSC), confirming that the polymers are ABA-type block copolymers. The identities of the molecular weights predetermined and which determined by GPC show the success of predetermining molecular weights of the polymers and preparing well-defined polymers. The narrow polydispersities, 1.1–1.3, indicate that the chains are propagating by a living mechanism. © 1993 John Wiley & Sons, Inc.     

Dipole moments of poly(ethylene oxide) and poly(hexamethylene oxide) chains

The mean-square dipole moments of poly(ethylene oxide) and poly(hexamethylene oxide) chains have been determined from dielectric constant measurements on dilute solutions of the polymers in benzene. The values obtained are in good agreement with those predccted using the rotational isomeric state models for these chains. In addition, the unperturbed dimensions of poly(hexamethylene oxide) have been calculated as a function of molecular weight, using the isomeric state theory.