Dynamic Response of Stereoblock Elastomeric Polypropylene Studied by Rheooptics and X-ray Scattering. 2. Orthogonally Oriented Crystalline Chains

Wiyatno, Willy; Pople, John A.; Gast, Alice P.; Waymouth, Robert M.; Fuller, Gerald G.

doi:10.1021/ma020262g

Cited by 15 publications

(32 citation statements)

References 49 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Recently, a unique orthogonal orientation, where polymeric chains align perpendicular to the drawing direction, has been occasionally reported in heterogeneous systems such as block copolymers, immiscible blends and organic/inorganic composites. Several models involving the epitaxial crystallization,8–10 thermal shrinkage stress,11,12 confinement of crystal growth,13–21 and trans‐crystallization22,23 have been employed to interpret such a behavior. However, it has rarely occurred in homogenous systems.…”

Section: Introductionmentioning

confidence: 99%

Uniaxial Drawing of Poly[(R)‐3‐hydroxybutyrate]/Cellulose Acetate Butyrate Blends and Their Orientation Behavior

Park

Tanaka

Doi

et al. 2005

Macromolecular Bioscience

View full text Add to dashboard Cite

Miscible blends of PHB and CAB were prepared by the solvent-casting method with various blend compositions, and their orientation behavior was investigated during uniaxial drawing. X-ray analysis revealed that the orientation of the crystallizable PHB component in the drawn PHB/CAB blends was changed from c-axis-orientation to a-axis-orientation with increasing CAB content. The a-axis-orientation was a result from the a-axis-oriented crystal growth caused by the intramolecular nucleation and the confined crystal growth. For quantitative assessment of the chain orientation, the Hermans orientation functions of the two respective components were obtained from the polarized FT-IR measurements. The orientation function of pure PHB stretched to 5 times of its initial length was approximately 0.8. However the value decreased rapidly with increasing CAB content, and it turned to a negative value from 30 wt.-% CAB content. This indicates that the PHB chains were aligned perpendicular to the drawing direction. On the contrary, the value of the CAB component remained almost unchanged at about 0.1 regardless of the blend composition and the annealing time, indicating that the CAB chains were constantly oriented parallel to the drawing direction without any chain relaxation. In addition, SAXS analysis suggested that the lamellar stacking direction also changed from parallel to perpendicular in the stretching direction with increasing CAB content.

show abstract

Section: Introductionmentioning

confidence: 99%

Uniaxial Drawing of Poly[(R)‐3‐hydroxybutyrate]/Cellulose Acetate Butyrate Blends and Their Orientation Behavior

Park

Tanaka

Doi

et al. 2005

Macromolecular Bioscience

View full text Add to dashboard Cite

show abstract

“…In situ birefringence and X-ray scattering data for ePP show a crystalline-to-mesomorphic microstructural transformation as the film is tensile drawn, similar to sPP [77][78][79][80] . In addition to confirming the presence and orientation behavior of iPP crystal morphs and mesomorphs (as observed with rheo-birefringence, small-angle, and wide-angle X-ray scattering), the rheo-FTIR spectrometer will provide equivalent information for the amorphous atactic segments simultaneously.…”

Section: Discussionmentioning

confidence: 80%

A Rheo-Optical FTIR Spectrometer for Investigating Molecular Orientation and Viscoelastic Behavior in Polymers

Hofmann

Sevegney

Kannan

2004

International Journal of Polymer Analysis and Characterization

View full text Add to dashboard Cite

A rheo-optical Fourier transform infrared (FTIR) spectrometer has been developed by combining step-scan FTIR spectroscopy with elements of polarimetry and rheometry in order to investigate both deformationinduced morphology changes and orientation=relaxation dynamics of components within complex polymers. This versatile instrument can directly and sensitively measure quantitative infrared spectra at different temperatures and for different deformation modes. A complex, multiplemodulation=demodulation processing scheme is used to extract both absorbance and dichroism information from a single detector signal. Experimental results from a semicrystalline isotactic polypropylene and a thermoplastic polyurethane are reported in order to illustrate instrument capabilities. INTRODUCTIONEstablishing the relationships between molecular structure and macromechanical (bulk) properties in polymers is an important task in the field of materials science and engineering. Such an understanding is becoming even more critical with emerging synthesis and processing technologies, where property manipulation at microscopic, and even nanoscopic, length scales is desired. Our recent efforts focus on understanding the dynamic behavior of individual chemical functionalities and microstructures within complex polymers as they undergo important processing steps. Specifically, we are studying both changes in morphology (over a range of length scales) and molecular orientation= relaxation responses that are induced by a mechanical perturbation of the bulk material. For example, the morphology of a semicrystalline polymer depends on stereochemical regularity, thermal history, and mechanical processing history [1,2] . Consequently, chemically identical polymers can possess different microstructures (e.g., crystalline, amorphous, mesophase), each responding quite differently to macroscopic deformation.Optical methods such as birefringence [3][4][5][6] , X-ray scattering [7][8][9][10][11][12] , and vibrational spectroscopy [13][14][15][16][17] have been used to characterize morphology and molecular orientation in polymers. Each aforementioned technique presents some subtle experimental limitation(s) that can be overcome using rheo-optical Fourier transform infrared (FTIR) spectroscopy. Rheo-FTIR involves the quantitative measurement of anisotropic absorbance (i.e., dichroism) spectra in order to investigate the local polymer physics responsible for macroscopic viscoelastic behavior. Absorption of infrared radiation is sensitive to individual moieties within polymers and thus serves as a good vibrational probe. Linear dichroism-the anisotropic absorption by a material of two mutually perpendicular states of linearly polarized light-has been recognized as a measure of orientation anisotropy on a molecular or submolecular scale [18][19][20] . Changes in orientation of different structures within a polymer, as well as morphology changes from one type of structure to another, may be driven by a macromechanical perturbation.We have developed a versati...

show abstract

“…This is plausible since the crystals are solid with a Young's modulus of 40 GPa along the chain direction, 45 and the amorphous matrix is viscoelastic at room temperature. 40,46,47 Furthermore, this mother lamella widens perpendicular to the stretching direction from 631 nm at ε = 0% to 701 nm at ε = 40%.…”

Section: Resultsmentioning

confidence: 93%

“…The deformation behavior of the crystal complex shown in Figure a and b resembles a tree branch that is pulled through a highly viscous liquid. This is plausible since the crystals are solid with a Young’s modulus of 40 GPa along the chain direction, and the amorphous matrix is viscoelastic at room temperature. ,, Furthermore, this mother lamella widens perpendicular to the stretching direction from 631 nm at ε = 0% to 701 nm at ε = 40%.…”

Section: Resultsmentioning

confidence: 99%

“…This time is much larger than the time constant of stress relaxation in ePP, which ranges between 10 s and 30 min. 46,47 Some very interesting and open questions in this context are the roles of molecular conformations within the amorphous phase, the topology of the network formed by the entanglements and polymer chains anchored in the crystalline regions, and the deformations of the molecular network upon stretching the film. Large-scale computer simulations based on molecular dynamics and/or Monte Carlo methods are required to resolve these questions.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Locally Auxetic Behavior of Elastomeric Polypropylene on the 100 nm Length Scale

Franke

Magerle

2011

ACS Nano

View full text Add to dashboard Cite

We observe unexpected locally auxetic behavior in elastomeric polypropylene, a semicrystalline polymer with a natural microstructure and a low degree of crystallinity. Our series of scanning force microscopy images show the nanomechanical deformation processes that occur upon stretching a thin film of elastomeric polypropylene. Upon uniaxial stretching, the angle between epitaxially grown lamella branches remains constant and the lamellae elongate, resulting in locally auxetic behavior (negative Poisson's ratio) on the 100-nanometer scale. This mechanism causing auxetic behavior, which was previously proposed on the basis of geometric arguments, appears to be an intrinsic property of certain semicrystalline polymers.

show abstract

Dynamic Response of Stereoblock Elastomeric Polypropylene Studied by Rheooptics and X-ray Scattering. 2. Orthogonally Oriented Crystalline Chains

Cited by 15 publications

References 49 publications

Uniaxial Drawing of Poly[(R)‐3‐hydroxybutyrate]/Cellulose Acetate Butyrate Blends and Their Orientation Behavior

Uniaxial Drawing of Poly[(R)‐3‐hydroxybutyrate]/Cellulose Acetate Butyrate Blends and Their Orientation Behavior

A Rheo-Optical FTIR Spectrometer for Investigating Molecular Orientation and Viscoelastic Behavior in Polymers

Locally Auxetic Behavior of Elastomeric Polypropylene on the 100 nm Length Scale

Contact Info

Product

Resources

About