The Reactive Formation of Diblock Copolymer at a Polymer/Polymer Interface and its Effect on Interfacial Structure

2000 ◽  
Vol 629 ◽  
Author(s):  
Jonathan S. Schulze ◽  
Timothy P. Lodge ◽  
Christopher W. Macosko
Keyword(s):  
Molecular Weight ◽  
Interfacial Structure ◽  
Root Mean Square Roughness ◽  
Radius Of Gyration ◽  
Interfacial Region ◽  
Force Microscopy ◽  
Amino Terminal ◽  
Polymer Interface ◽  
Atomic Force ◽  
Time Required

ABSTRACTThe reaction of perdeuterated amino-terminal polystyrene (dPS-NH2) with anhydrideterminal poly(methyl methacrylate) (PMMA-anh) at a PS/PMMA interface has been observed with forward recoil spectrometry (FRES). Bilayer samples were constructed by placing thin films of PS containing ∼8.5 wt % dPS-NH2 on a PMMA-anh layer. Significant reaction was observed only after annealing the samples at 174°C for several hours, a time scale at least two orders of magnitude greater than the time required for the dPS-NH2 chains to diffuse through the bulk PS layer. The topography of the interfacial region as copolymer formed was measured using atomic force microscopy (AFM). Roughening of the PS/PMMA interface was observed to varying degrees in all annealed samples. Furthermore, the extent of this roughening was found to depend on the PS matrix molecular weight. Reaction in the samples with a high molecular weight PS matrix resulted in a root mean square roughness approximately equal to the radius of gyration Rg of the copolymer. However, approximately twice as much roughening was observed in the low molecular weight PS matrix. This study reveals how the molecular weight of one of the phases can affect the rate of reaction at a polymer/polymer interface.

Low Molecular Weight Microfibers with Light Sensing Properties

2017 ◽  
Vol 54 (4) ◽  
pp. 655-658
Author(s):  
Andrei Bejan ◽  
Dragos Peptanariu ◽  
Bogdan Chiricuta ◽  
Elena Bicu ◽  
Dalila Belei
Keyword(s):  
Molecular Weight ◽  
Low Molecular Weight ◽  
X Ray Diffraction ◽  
Aromatic Rings ◽  
X Ray ◽  
Force Microscopy ◽  
Light Sensing ◽  
Sensing Applications ◽  
Atomic Force ◽  
Low Molecular Weight Compounds

Microfibers were obtained from organic low molecular weight compounds based on heteroaromatic and aromatic rings connected by aliphatic spacers. The obtaining of microfibers was proved by scanning electron microscopy. The deciphering of the mechanism of microfiber formation has been elucidated by X-ray diffraction, infrared spectroscopy, and atomic force microscopy measurements. By exciting with light of different wavelength, florescence microscopy revealed a specific optical response, recommending these materials for light sensing applications.

Breaking Down the Supramolecular Ensemble: Single-Molecule Studies of the Concentration Dependence of Main-Chain Supramolecular Polymer Molecular Weight Distributions on Surfaces

2010 ◽  
Vol 63 (4) ◽  
pp. 624
Author(s):  
Michael J. Serpe ◽  
Jason R. Whitehead ◽  
Stephen L. Craig
Keyword(s):  
Molecular Weight ◽  
Single Molecule ◽  
Monomer Concentration ◽  
Supramolecular Polymer ◽  
Force Microscopy ◽  
Molecular Weight Distributions ◽  
Atomic Force ◽  
Multi Stage ◽  
Single Molecule Studies ◽  
Supramolecular Ensemble

Single molecule atomic force microscopy (AFM) studies of oligonucleotide-based supramolecular polymers on surfaces are used to examine the molecular weight distribution of the polymers formed between a functionalized surface and an AFM tip as a function of monomer concentration. For the concentrations examined here, excellent agreement with a multi-stage open association model of polymerization is obtained, without the need to invoke additional contributions from secondary steric interactions at the surface.

Scratching the surface: Imaging interfacial structure using atomic force microscopy

Food Colloids ◽  
2007 ◽  
pp. 13-21 ◽  
Author(s):  
Alan R. Mackie ◽  
A. Patrick Gunning ◽  
Peter J. Wilde ◽  
Victor J. Morris
Keyword(s):  
Atomic Force Microscopy ◽  
Interfacial Structure ◽  
Surface Imaging ◽  
Force Microscopy ◽  
Atomic Force

Stereocomplex electrospun fibers from high molecular weight of poly(L-lactic acid) and poly(D-lactic acid)

2020 ◽  
Vol 40 (2) ◽  
pp. 136-142 ◽  
Author(s):  
Homa Maleki ◽  
Hossein Barani
Keyword(s):  
Molecular Weight ◽  
Lactic Acid ◽  
Thermal Properties ◽  
High Molecular Weight ◽  
Chemical Properties ◽  
Electrospun Fibers ◽  
Scanning Calorimetry ◽  
Force Microscopy ◽  
Atomic Force ◽  
Electrospinning Method

AbstractThe stereocomplex formation is a promising method to improve the properties of poly(lactide) (PLA)-based products due to the strong interaction of the side-by-side arrangement of the molecular chains. Recently, electrospinning method has been applied to prepare PLA stereocomplex, which is more convenient. The objective of the current study is to make stereocomplexed PLA nanofibers using electrospinning method and compare their properties and structures with pure poly(l-lactide) (PLLA) fibers. The stereocomplexed fibers were electrospun from a blend solution of high molecular weight PLLA and poly(d-lactide) (1:1 ratio). The morphology of the obtained electrospun fibers was examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Differential scanning calorimetry was applied to study their thermal properties and crystallinity. Fourier transform infrared spectroscopy (FTIR) test was conducted on the samples to characterize their chemical properties. The SEM and AFM images indicated that smooth uniform fibers with a cylindrical structure were produced. Besides, the FTIR results and thermal properties confirmed that only stereocomplex crystallites formed in the resulting fibers via the electrospinning method.

Surface Instability and Associated Roughness of Pendeo-epitaxy GaN (0001) Films Grown via Metalorganic Vapor Phase Epitaxy

2001 ◽  
Vol 693 ◽  
Author(s):  
Amy M. Roskowski ◽  
Peter Q. Miraglia ◽  
Edward A. Preble ◽  
Sven Einfeldt ◽  
Robert F. Davis
Keyword(s):  
Smooth Surface ◽  
Growth Process ◽  
Root Mean Square Roughness ◽  
Optimum Temperature ◽  
Force Microscopy ◽  
Atomic Force ◽  
Process Route ◽  
Vertical Growth Rate ◽  
Hillock Growth ◽  
Sidewall Surface

AbstractA growth process route that results in thin film GaN templates with a smooth surface morphology at the optimum temperature of 1020°C has been developed. Atomic force microscopy (AFM) reveals hillocks on films grown above 1020°C. Hillocks resulted from the rotation of heterogeneous steps formed at pure screw or mixed dislocations which terminated on the (0001) surface. Growth of the latter feature was controlled kinetically by temperature through adatom diffusion. The 106 cm-2 density of the hillocks was reduced through growth on thick GaN templates and regions of pendeo-epitaxy (PE) overgrowth with lower pure screw or mixed dislocations. Smooth PE surfaces were obtained at temperatures that reduced the lateral to vertical growth rate but also retarded hillock growth that originated in the stripe regions. The (1120 ) PE sidewall surface was atomically smooth, with a root mean square roughness value of 0.17 nm which was the noise limited resolution of the AFM measurements.

scholarly journals The Molecular Weight Dependence of Thermoelectric Properties of Poly (3-Hexylthiophene)

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1404 ◽  
Author(s):  
Saeed Mardi ◽  
Marialilia Pea ◽  
Andrea Notargiacomo ◽  
Narges Yaghoobi Nia ◽  
Aldo Di Carlo ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Molecular Weight ◽  
Seebeck Coefficient ◽  
Thermoelectric Properties ◽  
Thermoelectric Power Factor ◽  
Force Microscopy ◽  
Atomic Force ◽  
Molecular Weight Dependence ◽  
Vis Spectroscopy ◽  
Afm Analysis

Organic materials have been found to be promising candidates for low-temperature thermoelectric applications. In particular, poly (3-hexylthiophene) (P3HT) has been attracting great interest due to its desirable intrinsic properties, such as excellent solution processability, chemical and thermal stability, and high field-effect mobility. However, its poor electrical conductivity has limited its application as a thermoelectric material. It is therefore important to improve the electrical conductivity of P3HT layers. In this work, we studied how molecular weight (MW) influences the thermoelectric properties of P3HT films. The films were doped with lithium bis(trifluoromethane sulfonyl) imide salt (LiTFSI) and 4-tert butylpyridine (TBP). Various P3HT layers with different MWs ranging from 21 to 94 kDa were investigated. UV–Vis spectroscopy and atomic force microscopy (AFM) analysis were performed to investigate the morphology and structure features of thin films with different MWs. The electrical conductivity initially increased when the MW increased and then decreased at the highest MW, whereas the Seebeck coefficient had a trend of reducing as the MW grew. The maximum thermoelectric power factor (1.87 μW/mK2) was obtained for MW of 77 kDa at 333 K. At this temperature, the electrical conductivity and Seebeck coefficient of this MW were 65.5 S/m and 169 μV/K, respectively.

Analysis of randomly oriented structures by grazing-incidence small-angle neutron scattering

2012 ◽  
Vol 45 (2) ◽  
pp. 245-254 ◽  
Author(s):  
Denis Korolkov ◽  
Peter Busch ◽  
Lutz Willner ◽  
Emmanuel Kentzinger ◽  
Ulrich Rücker ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Small Angle ◽  
Diblock Copolymers ◽  
Weight Fraction ◽  
Grazing Incidence ◽  
Force Microscopy ◽  
Self Organized ◽  
Atomic Force ◽  
Instrumental Resolution ◽  
Evaluation Of Data

A formalism is presented which allows the quantitative evaluation of data from grazing-incidence small-angle neutron and X-ray scattering – GISANS and GISAXS – in the framework of the distorted wave Born approximation. While several aspects have been reported previously, this formalism combines solutions for scattering intensities in both reflection and transmission hemispheres, taking into account instrumental resolution effects. This formalism is applied to the case of GISANS from self-organized diblock copolymers, ordered in perpendicular lamellar structures on an Si wafer in randomly oriented short-range-ordered regions. The periodicity ofD= 85 (9) nm found for deuterated polystyrene–polybutadiene of molecular weight  Mw= 165 kg mol−1and a molecular weight fraction of the deuterated polystyrene block of 52% is consistent with atomic force microscopy and specular neutron reflectivity results.

Synthesis of polystyrene-grafted carbon nanocapsules

2007 ◽  
Vol 22 (1) ◽  
pp. 132-140 ◽  
Author(s):  
Hsuan-Ming Huang ◽  
Hung-Chieh Tsai ◽  
I-Chun Liu ◽  
Raymond Chien-Chao Tsiang
Keyword(s):  
Electron Microscopy ◽  
Molecular Weight ◽  
Polymeric Composite ◽  
Decomposition Temperature ◽  
Polymeric Composite Material ◽  
Scanning Calorimetry ◽  
Force Microscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
Carbon Nanocapsules

A novel polymeric composite material, polystyrene (PS)-grafted carbon nanocapsules (CNCs), has been prepared. sec-butyllithium was first used to introduce negative charges on CNCs, and these CNC carbanions acted then as initiators for anionic polymerization of styrene. Based on a weight loss at the decomposition temperature of the butyl groups, the quantity of the butyls attached to the CNC surface was determined as 1.18 wt%, corresponding to 0.25 mol% initiator per mol of carbon atom on the CNC surface. Furthermore, the decomposition temperature of butylated CNCs was lower than that of the pristine CNCs by nearly 200 °C. The polystyrene content in our PS-grafted CNC sample was approximately 20%, and the molecular weight of the grafted PS on the surface of CNCs was calculated as 1200 gmol−1. Compared with the molecular weight of the ungrafted PS, the molecular weight of grafted PS was lower, thus indicating rates of initiation and/or propagation for CNC-bound carbanions lower than those of the free sec-butyllithium. The PS-grafted CNCs had good dispersion in toluene, tetrahydrofuran, cyclohexane, and other common organic solvents in which polystyrene was dissolvable and thus indicated good compatibility when further blended with other styrenic polymers. The PS-grafted CNCs were characterized and examined by Fourier transform infrared, thermogravimetric analysis, atomic force microscopy, differential scanning calorimetry, ultraviolet-visible spectroscopy, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. The electron microscopy images indicated that the PS-grafted CNCs were homogeneous composites containing uniform polymer/CNC ratios.

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