Preparation of High Polymers

Roff, W.J.

doi:10.1016/b978-0-408-15960-9.50053-x

Cited by 13 publications

(15 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…There does, however, seem to be a slight rounding of the curve at the transition point upon expansion. This lack of qualitative hysteresis indicates relatively quick relaxation dynamics, as expected from the low glass transition of PnBA ( T g ≈ −55 °C), and a likely lack of entanglements in collapsed monolayer.…”

Section: Analysis and Discussion Of Experimental Resultsmentioning

confidence: 83%

“…In this work we report a study of the surface structures and properties of poly( n -butyl acrylate), which is a soft amorphous polymer, T g = −55 °C, and belongs in Crisp’s first group, through all four surface coverage regimes. This is the first such study of a soft polymer in the near theta condition (as will be discussed below) for such a wide range of surface coverages.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Formation and Collapse of Single-Monomer-Thick Monolayers of Poly(n-butyl acrylate) at the Air−Water Interface

et al. 2010

View full text Add to dashboard Cite

The behavior of poly(n-butyl acrylate) (PnBA) spread at the air-water interface has been studied for a full range of surface coverages and several molecular weights. At low and intermediate surface coverages, the surface pressure-area isotherm behavior of the polymer is found to follow the expected scaling laws. In the dilute regime the pressure is an increasing function of surface coverage and a decreasing function of molecular weight. In the semidilute regime the surface pressure becomes independent of molecular weight, and a Flory exponent for the twodimensional radius of gyration is found to be ν = 0.57 ( 0.02. Beginning in the high coverage concentrated regime, at a surface pressure of around 15 mN/m, and through the full coverage regime (where the water in the subphase is fully covered and not exposed to air), X-ray reflectivity (XR) measurements show the formation of a continuous waterfree monolayer (i.e., one monomer thick) film of the polymer. At surface concentrations above the transition point to the full coverage regime (alternatively called the "collapsed" regime hereafter for the reason that will become apparent below), Brewster angle microscopy (BAM) shows that the excess polymer material does not distribute uniformly in the polymer film layer but instead leads to formation of micrometer-scale isolated globular domains of roughly uniform size. Further, it was observed that the number of such domains increases as the surface polymer concentration is increased, whereas the size of the globular domains is largely unaffected by the concentration variation. X-ray grazing incidence diffraction (GID) indicates that these domains are regions of bulklike (amorphous) polymer. These and other observations, including the invariant nature of the monolayer throughout the compression (confirmed by XR), the plateau nature of surface pressure-area isotherm throughout the collapsed regime, and the reversible nature of the domain formation (evidenced by BAM), suggest that the globular domains formed at high surface concentrations of PnBA are in a type of coexistence with the uniform monolayer. A simple thermodynamic model considering the entropic penalty of confining the polymer chains to monolayer, the translational entropy of the domains, and the surface energy of the interface is made in order to understand the behavior of the polymer as it becomes excluded from the monolayer. This argument suggests that the excess polymer should form a single large domain in order to minimize the large surface energy at the water-polymer interface. The presence of many small domains suggests the domains are kinetically trapped in a local, rather than global, equilibrium.

show abstract

Section: Analysis and Discussion Of Experimental Resultsmentioning

confidence: 83%

Section: Introductionmentioning

confidence: 99%

Formation and Collapse of Single-Monomer-Thick Monolayers of Poly(n-butyl acrylate) at the Air−Water Interface

et al. 2010

View full text Add to dashboard Cite

show abstract

“…The smooth shape of the isotherm curve at areas <170 Å 2 per chain suggests that it is unlikely that the slope transition is due to the formation of wrinkled (crumpled) structures and subsequent loss of material into the subphase; the formation of wrinkles and irreversible loss of polymer would produce oscillatory surface pressure signals . We suspect that the (near) constancy of surface pressure at surface areas <170 Å 2 per chain is an indication of a thermodynamic phase transition (likely of the first order) that occurs within the PEG brush layer due to the many-body attractive interactions among the PEG segments (termed in the literature as the “ n -cluster” effects). , At the position of the slope break, the maximum PEG volume fraction within the brush layer is estimated to be approximately 0.45 (near the grafting surface), which is in reasonable agreement with theoretical predictions. , Indirect experimental evidence for the “ n -cluster”effects has previously been reported in the literature in terms of the thickness properties and the rheological properties of PEG brush systems. To our knowledge, a slope change in the isotherm of PEG-containing monolayers has not previously been identified as an indication of phase transition.…”

Section: Results and Discussionmentioning

confidence: 99%

Surface Mechanical and Rheological Behaviors of Biocompatible Poly((d,l-lactic acid-ran-glycolic acid)-block-ethylene glycol) (PLGA–PEG) and Poly((d,l-lactic acid-ran-glycolic acid-ran-ε-caprolactone)-block-ethylene glycol) (PLGACL–PEG) Block Copolymers at the Air–Water Interface

et al. 2015

View full text Add to dashboard Cite

Air-water interfacial monolayers of poly((D,L-lactic acid-ran-glycolic acid)-block-ethylene glycol) (PLGA-PEG) exhibit an exponential increase in surface pressure under high monolayer compression. In order to understand the molecular origin of this behavior, a combined experimental and theoretical investigation (including surface pressure-area isotherm, X-ray reflectivity (XR) and interfacial rheological measurements, and a self-consistent field (SCF) theoretical analysis) was performed on air-water monolayers formed by a PLGA-PEG diblock copolymer and also by a nonglassy analogue of this diblock copolymer, poly((D,L-lactic acid-ran-glycolic acid-ran-caprolactone)-block-ethylene glycol) (PLGACL-PEG). The combined results of this study show that the two mechanisms, i.e., the glass transition of the collapsed PLGA film and the lateral repulsion of the PEG brush chains that occur simultaneously under lateral compression of the monolayer, are both responsible for the observed PLGA-PEG isotherm behavior. Upon cessation of compression, the high surface pressure of the PLGA-PEG monolayer typically relaxes over time with a stretched exponential decay, suggesting that in this diblock copolymer situation, the hydrophobic domain formed by the PLGA blocks undergoes glass transition in the high lateral compression state, analogously to the PLGA homopolymer monolayer. In the high PEG grafting density regime, the contribution of the PEG brush chains to the high monolayer surface pressure is significantly lower than what is predicted by the SCF model because of the many-body attraction among PEG segments (referred to in the literature as the "n-cluster" effects). The end-grafted PEG chains were found to be protein resistant even under the influence of the "n-cluster" effects.

show abstract

“…An electro-optic modulator was used to gate pulses from the pulse train of repetition rate 80 MHz to 100 kHz and 1 kHz. No pronounced difference was observed once the repetition rate is below 1 kHz, because the inter-pulse separation is 1 ms, which is significantly longer than the heat diffusion time of microseconds 26 for the given focal region. The comparison of the averaged contrast of the 16 patterned bits normalized to that of the voids, as a result of deformation of the matrix, clearly revealed that the pulse energy that the sample can stand, or the dynamic range, is much broader at 1 kHz than that at higher repetition rates of 100 kHz and 80 MHz.…”

Section: Methodsmentioning

confidence: 95%

Three-dimensional orientation-unlimited polarization encryption by a single optically configured vectorial beam

et al. 2012

View full text Add to dashboard Cite

The interplay between light polarization and matter is the basis of many fundamental physical processes and applications. However, the electromagnetic wave nature of light in free space sets a fundamental limit on the three-dimensional polarization orientation of a light beam. Although a high numerical aperture objective can be used to bend the wavefront of a radially polarized beam to generate the longitudinal polarization state in the focal volume, the arbitrary three-dimensional polarization orientation of a beam has not been achieved yet. Here we present a novel technique for generating arbitrary three-dimensional polarization orientation by a single optically configured vectorial beam. As a consequence, by applying this technique to gold nanorods, orientation-unlimited polarization encryption with ultra-security is demonstrated. These results represent a new landmark of the orientation-unlimited three-dimensional polarization control of the light–matter interaction.

show abstract

Preparation of High Polymers

Cited by 13 publications

References 3 publications

Formation and Collapse of Single-Monomer-Thick Monolayers of Poly(n-butyl acrylate) at the Air−Water Interface

Formation and Collapse of Single-Monomer-Thick Monolayers of Poly(n-butyl acrylate) at the Air−Water Interface

Surface Mechanical and Rheological Behaviors of Biocompatible Poly((d,l-lactic acid-ran-glycolic acid)-block-ethylene glycol) (PLGA–PEG) and Poly((d,l-lactic acid-ran-glycolic acid-ran-ε-caprolactone)-block-ethylene glycol) (PLGACL–PEG) Block Copolymers at the Air–Water Interface

Three-dimensional orientation-unlimited polarization encryption by a single optically configured vectorial beam

Contact Info

Product

Resources

About