Infrared temperature studies of a simple polyurea

Coleman, Michael M.; Sobkowiak, Maria; Pehlert, George J.; Painter, Paul C.; Iqbal, Tahir

doi:10.1002/macp.1997.021980110

Cited by 148 publications

(153 citation statements)

References 18 publications

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“…In the amine region, a broad peak centered at around 3335cm À1 , corresponding to N-H stretching in hydrogen bonded urea groups [12] grows with the increase in urea group concentration that takes place with the decrease on the PCL length or decrease in PCL fraction in SPUUs (see Table 1), as expected. We do not see any evidence of free (non-hydrogen bonded) N-H groups (vibrations to be found at approximately 3450 cm À1 ) [13] . Thus, urethane urea formation has been confirmed from IR analysis.…”

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confidence: 94%

Controlled Release of Model Drug from Biodegradable Segmented Polyurethane Ureas: Morphological and Structural Features

Reddy

Hadano

Takahara

2006

Macromolecular Symposia

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Summary: Segmented polyurethane ureas (SPUUs), which are being used in implant devices, were evaluated as drug delivery matrices using theophylline as a model drug without much sacrificing the mechanical properties of films after drug doping. SPUUs were synthesized from aliphatic diisocyanate (lysine methyl ester diisocyante (LDI)), poly(caprolactone) diol with molecular weights 530, 1250 and 2000 and 1,4-butanediamine. Three series of segmented SPUUs were prepared with various soft segment lengths and were characterized by Fourier transform infrared spectroscopy, dynamic viscoelastic measurements and tensile testing. A single tand peak was observed in dynamic viscoelastic measurements, which revealed phase mixing of hard and soft segments. Low elongation at break was observed in case of PCL 2000 based SPUUs, may be due to partial cystallization of PCL segment. The degradation of SPUUs in alkaline solution and in vitro drug release of theophylline in pH 7.4 buffer were also investigated. The drug release behavior from these films were analyzed by the exponent relation M t /M 1 ¼ kt n , where k and n are constants and M t /M 1 is the fraction of drug released until time, t. The constant n was found to be close to 0.5 in all samples, which suggests the release of drug from these polymers can be explained by the Fickian diffusion model.

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confidence: 94%

Controlled Release of Model Drug from Biodegradable Segmented Polyurethane Ureas: Morphological and Structural Features

Reddy

Hadano

Takahara

2006

Macromolecular Symposia

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“…Model studies indicate that crystalline urea compounds show a well-defined absorption peak at 1640 cm Ϫ1 . 42,43 This has been attributed to a urea carbonyl that is hydrogen bonded to two N-H groups of another urea segment. Frequency and apparent intensity of this 1640 cm Ϫ1 band depend on magnitude and specificity of interatomic interactions.…”

Section: Resultsmentioning

confidence: 98%

“…The disordered sample, in contrast, had a broad absorption centered at 1650 cm Ϫ1 . 42 Based on our infrared data, we would suggest that hard segment-rich domains in samples prepared at low temperatures are very well organized. In contrast, samples prepared at 150°C possess a more disordered or dispersed structure.…”

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confidence: 95%

Direct observation of morphological differences as a function of reaction temperature in model systems for polyurethane foams

Yontz¹,

Hsu²,

Lidy³

et al. 1998

J. Polym. Sci. B Polym. Phys.

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A series of polyurea urethanes was isothermally synthesized from toluene diisocyanate (TDI), water, and trifunctional poly(propylene oxide) in the temperature range of 50–150°C. Morphologies of the samples vary significantly as a function of reaction temperature. In this system, phase separation competes with polymerization and crosslinking. Both transmission electron microscopy and atomic force microscopy have shown a network type of structure for the 50°C samples, while the 150°C samples appear to be homogeneous. Infrared analysis shows that samples prepared at 150°C possess a morphology that is less strongly hydrogen bonded and has a broader distribution of hydrogen‐bonded states compared to those prepared at lower temperatures. From this combination of techniques, it can be inferred that phase separation occurs faster than crosslinking at low temperatures; consequently, a phase‐separated morphology forms. In contrast, crosslinking occurs faster than phase separation at higher reaction temperatures. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 3065–3077, 1998

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“…The microphase-separated segmented block copolymer morphology consists of hard segment domains dispersed in a soft matrix. [12][13][14] The hard domains are extensively hydrogen-bonded 15,16 and function as both reversible physical cross-links and a reinforcing filler, thus providing good mechanical properties, especially toughness. [17][18][19][20] Mechanisms proposed for the enhanced performance of PU-coated substrates include a delay in the onset of necking in the substrate, 1 an impact-induced transition to a glassy state of the PU soft segments, 2 and retardation of compression waves transmitted to the substrate.…”

Section: Introductionmentioning

confidence: 99%

Structure Evolution in a Polyurea Segmented Block Copolymer Because of Mechanical Deformation

et al. 2008

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Extensional stress-strain measurements on a polyurea (PU) were carried out at strain rates up to 830 s -1 , in combination with ex post facto small-angle X-ray scattering (SAXS) measurements and temperaturedependent SAXS. The elastomer is of interest because of its application as an impact-resistant coating. The highest strain rates used herein fall within the softening, or transition, zone of the viscoelastic spectrum and are thus relevant to the working hypothesis that the performance of a polyurea impact coating is related to its transition to the glassy state when strained very rapidly. While quasi-static and slow deformation of the PU gives rise to irrecoverable strain and anisotropic SAXS patterns, when stretched at high rates the PU recovers completely and the scattering is isotropic. Thus, the deformation of the hard domains observed at low rates is absent at high strain rates. Linear dynamic mechanical measurements were also carried out, with the obtained segmental relaxation times in good agreement with dielectric relaxation measurements on this material. The PU exhibits the usual breakdown of time-temperature superposition in the transition zone. This thermorheological complexity underlies the fact that published time-temperature shift factors for this material are unrelated to the segmental dynamics, and therefore use of these shift factors to predict the onset of glassy dynamics during impact loading of the PU will be in error.

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Infrared temperature studies of a simple polyurea

Cited by 148 publications

References 18 publications

Controlled Release of Model Drug from Biodegradable Segmented Polyurethane Ureas: Morphological and Structural Features

Controlled Release of Model Drug from Biodegradable Segmented Polyurethane Ureas: Morphological and Structural Features

Direct observation of morphological differences as a function of reaction temperature in model systems for polyurethane foams

Structure Evolution in a Polyurea Segmented Block Copolymer Because of Mechanical Deformation

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