Rapid integrated rheo-optical and polarized Fourier-transform infrared spectrometry measurement system for polymer films undergoing chemo-mechanical changes

Ünsal, Emre; Nugay, Isik Isil; Offenbach, I.; Gross, M.; Manning, Christopher J.; Çakmak, Mükerrem

doi:10.1063/1.4811845

Cited by 7 publications

(6 citation statements)

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“…A real-time mechano-optical measurement integrated with an ultrarapid-scan polarized Fourier-transform infrared spectrometer was used for this study. Details of the instrument are described elsewhere . The real-time stress, strain, and spectral birefringence were recorded and calculated in the same manner as described in the previous section.…”

Section: Experimental Sectionmentioning

confidence: 99%

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Nonlinear Mechano-Optical Behavior and Strain-Induced Structural Changes of l-Valine-Based Poly(ester urea)s

et al. 2018

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The uniaxial mechano-optical behavior of a series of amorphous L-valine-based poly(ester urea) (VAL-PEU) with varying diol lengths was studied to elucidate the molecular mechanism associated with their thermal shape memory properties. A custom, real-time measurement system was used to capture the true stress, true strain, and birefringence during the temporary shape programming at stretching temperatures above the glass transition temperature (T g ). The mechanooptical response of VAL-PEUs exhibits an initial photoelastic behavior related to enhanced segmental correlation at low temperatures above the T g . A characteristic temperature, defined as the liquid−liquid (T ll ) transition (rubbery−viscous transition), was found at about 1.05 T g (K) (at T g + 15 °C) at strain rate of 0.017 s −1 , above which the segmental contacts largely "melt" and the initial slope of the stress-optical curves becomes temperature independent. This temperature corresponds to the temperature where mean relaxation time for the polymer is maximized. Real-time infrared spectroscopy (IR) and in situ wideangle X-ray scattering (WAXS) revealed a strain-induced intersegmental structural change during stretching. The intermolecular hydrogen bonding between the urea−urea and/or urea−carbonyl groups was found to adopt different bonding modes at the onset of strain hardening with a concurrent increased separation distance between adjacent segments. The hydrogen bonding strengthened supramolecular packing. The compromised shape recovery is a result of the disruption of the rigid segmental correlation, induced either by large extension at T < T ll or by progressive thermal effects at T > T ll , both of which may be minimized at T ll .

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Section: Experimental Sectionmentioning

confidence: 99%

“…Details of the instrument are described elsewhere. 64 The real-time stress, strain, and spectral birefringence were recorded and calculated in the same manner as described in the previous section. Additionally, a disk mirror interferometer was used to record the infrared (IR) absorbance at a rate of 300 spectra/s.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Nonlinear Mechano-Optical Behavior and Strain-Induced Structural Changes of l-Valine-Based Poly(ester urea)s

et al. 2018

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“…A real-time mechano-optical measurement platform equipped with an ultrarapid-scan polarized FTIR spectrometer was used to probe the deformation behavior of polymer segments in the crystalline and amorphous domains separately. Details of the measurement technique are discussed elsewhere . In brief, the specimen was clamped to load cells in the uniaxial stretching machine and enclosed within a thermal chamber.…”

Section: Methodsmentioning

confidence: 99%

“…Details of the measurement technique are discussed elsewhere. 13 In brief, the specimen was clamped to load cells in the uniaxial stretching machine and enclosed within a thermal chamber. The stress−strain curves were calculated from the measured force and the true cross-sectional area of the deformed specimen, which was determined by measuring the real-time width of the specimen and assuming an incompressible deformation with transverse isotropy.…”

Section: ■ Introductionmentioning

confidence: 99%

Real-Time Infrared–Mechano-Optical Behavior and Structural Evolution of Polypropylene and Hydroxyl-Functionalized Polypropylene during Uniaxial Deformation

et al. 2015

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This paper focuses on the real-time mechano-optical behavior of hydroxyl-functionalized polypropylene (PPOH) copolymer containing 0.4 mol % comonomer of 10-hydroxy-1-undecene and its comparison with unmodified polypropylene (PP). The mechano-optical behavior of the two polymers was studied in the partially molten state during four different processing steps heating, stretching, annealing, and coolingwith an integrated system that combined uniaxial stretching with real-time spectral birefringence and real-time ultrarapid-scan polarized FTIR measurements. While the material response was dominated by the crystalline network in both polymers, the presence of intermolecular hydrogen bonding between the hydroxyl groups was found to affect the structural evolution of the PPOH copolymer more significantly compared to the PP homopolymer. The PPOH copolymer exhibited not only lower crystallinity and smaller crystals but also a lower extent of lamella thickening at similar deformation conditions due to steric hindrance by the copolymer C9−side chains and OH groups. Uniaxial deformation of PP up to lower strains (ε H ∼ 0.1) and subsequent cooling had the same effect on the crystal structure as annealing the polymer for longer times (≥30 min) at the same temperature with no deformation and subsequent cooling, which was a decrease in the population of smaller crystals and an increase in the average crystal size while maintaining similar crystallinity as the undeformed PP. Surprisingly, for PP both the amorphous and crystalline chain axes were oriented in the transverse direction (TD) at low strains before orienting in the machine direction (MD) at higher strains. However, no such observation was made for PPOH. This behavior was ascribed to the difference in breakup and unraveling of the spherulitic morphology between PP and PPOH upon deformation. In addition, four different regimes in the stress−optical curve were established for both the polymers. Stress relaxation immediately following uniaxial deformation of PP in the semimolten state resulted in a loss of MD orientation of crystalline segments but an increase in the MD orientation of amorphous segments. Unlike the result for PP, in PPOH the secondary H-bonded network supported the primary crystalline network during stress relaxation, and no change in the orientation of either crystalline or amorphous segments was observed. A schematic of the structural evolution was proposed based on the experimental results.

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“…Real-time birefringence is measured by spectral birefringence method. − The in-plane and out-of-plane birefringence is calculated by measuring the 0° and 45° retardation values. The optical light paths for these measurements are shown with yellow transparent tubes in the figure below.…”

Section: Methodsmentioning

confidence: 99%

Real-Time Characterization of Physical Changes in Polyimide Film Formation: From Casting to Imidization

Ünsal

Cakmak

2013

Macromolecules

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Drying and imidization of PMDA−ODA solutions in NMP were investigated by a novel custom designed measurement system that tracks real time weight, thickness, surface temperature, and in-plane and out-of-plane birefringence. At low temperature drying stage, the weight and thickness reductions occurred rapidly as a result of solvent evaporation. All the parameters started leveling off while the out of plane birefringence steadily increased and reached a plateau at longer drying times. When the temperature was increased for imidization reaction, additional weight loss accompanied by temporary reduction of birefringence was observed due to evaporation of bound solvent as solvent molecules decomplexed from the polymer chains and plasticized the film. During the latter stage, out-of-plane birefringence rose rapidly due to increased intrinsic birefringence of the polymer chains due to imidization reaction and orientation of polymer chains with their chain axes preferentially oriented in the film plane. Throughout the whole process the in-plane birefringence remained zero. For the first time, these real time measurements allowed us to quantitatively show the dynamics between chain relaxation due to evaporation of the decomplexed solvent molecules, and orientation development due to decreased chain mobility caused by imidization reaction and increasing T g for the PMDA− ODA/NMP solutions. In addition, the dynamics of this interplay was investigated by varying the processing conditions: initial casting thickness and drying temperature.

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Rapid integrated rheo-optical and polarized Fourier-transform infrared spectrometry measurement system for polymer films undergoing chemo-mechanical changes

Cited by 7 publications

References 71 publications

Nonlinear Mechano-Optical Behavior and Strain-Induced Structural Changes of l-Valine-Based Poly(ester urea)s

Nonlinear Mechano-Optical Behavior and Strain-Induced Structural Changes of l-Valine-Based Poly(ester urea)s

Real-Time Infrared–Mechano-Optical Behavior and Structural Evolution of Polypropylene and Hydroxyl-Functionalized Polypropylene during Uniaxial Deformation

Real-Time Characterization of Physical Changes in Polyimide Film Formation: From Casting to Imidization

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