Direct Observation of Poly(propylene)-block-Poly(ethylene-co-propylene) Molecules by Atomic Force Microscopy (original) (raw)
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A Scanning Force Microscopy Study of Block Copolymers Containing a Conjugated Segment
MRS Proceedings, 1997
Atomic Force Microscopy (AFM) and related techniques are used to investigate the morphology of diblock copolymers. We focus on compounds containing a conjugated segment, polyparaphenylene, associated to a polymethylmethacrylate or a polystyrene block. The influence of the presence of the conjugated segment on the microdomain morphology is analyzed as a function of chain composition. Separate microdomains are observed on the surface of thin films by means of phase-detection imaging tapping-mode AFM. Their shape and size are interpreted in terms of molecular aggregation, with the help of molecular dynamics calculations.
Synthetic Metals, 2003
Polydisperse (M w /M n = 2.4) rod-coil, multi-block poly(polymethylphenylsilane-block-polyisoprene) (PMPS-b-PI), containing semiconductor segments, was characterised using atomic force microscopy (AFM) and neutron scattering. Despite high polydispersities (M w /M n (PMPS) = 1.64; M w /M n (PI) = 1.34) resulting in disorder, solid-state PMPS-b-PI was indicated to form a regular, modulated morphology with average domain repeat unit of 18.8 nm at the surface (AFM) and 18.6 nm in the bulk (neutron). The observed regularity was tentatively proposed to result from a lamella-like morphology preferred by rod-coil, multi-block copolymers and the helical, segmental geometry of PMPS. This tentative theory was corroborated by good agreement between expected and found domain sizes, which indicated that copolymers did not, to a recognisable extent, fold and reverse direction.
Microphase separation at the surface of block copolymers, as studied with atomic force microscopy
Colloids and Surfaces B: Biointerfaces, 2000
Atomic force microscopy (AFM) is used to study the phase separation process occurring in block copolymers in the solid state. The simultaneous measurement of the amplitude and the phase of the oscillating cantilever in the tapping mode operation provides the surface topography along with the cartography of the microdomains of different mechanical properties. This technique thus allows to characterize the size and shape of those microdomains and their organization at the surface (e.g. cubic lattice spheres, hexagonal lattice of cylinders, or lamellae). In this study, a series of symmetric triblock copolymers made of a inner elastomeric sequence (poly(butadiene) or poly(alkylacrylate)) and two outer thermoplastic sequences (poly(methylmethacrylate)) is analyzed by AFM in the tapping mode. The microphase separation and their morphology are essential factors for the potential of these materials as a new class of thermoplastic elastomers. Special attention is paid to the control of the surface morphology, as observed by AFM, by the molecular structure of the copolymers (volume ratio of the sequences, molecular weight, length of the alkyl side group) and the experimental conditions used for the sample preparation. The molecular structure of the chains is completely controlled by the synthesis, which relies on the sequential living anionic polymerization of the comonomers. The copolymers are analyzed as solvent-cast films, whose characteristics depend on the solvent used and the annealing conditions. The surface arrangement of the phase-separated elastomeric and thermoplastic microdomains observed on the AFM phase images is discussed on the basis of quantitative information provided by the statistical analysis by Fourier transform and grain size distribution calculations.
Atomic force microscopy investigation of asymmetric diblock copolymer morphologies in thin films
European Polymer Journal, 2004
Microphase separation and the resulting morphology of asymmetric diblock copolymers of poly(e-caprolactone) (PCL) in thin films have been investigated by atomic force microscopy. Copolymers consisted of a short block of PCL (M n $ 2500-4500 g/mole) and a longer second block of poly(methyl methacrylate) (PMMA), poly(styrene) (PS) or poly(cyclohexene oxide) (PCHO). Tendency for microphase separation above the glass transition temperature of the second block (PMMA, PS or PCHO) resulted in a pitted morphology on the surface of the thin films. This tendency was strongest for PMMA and weakest for PCHO. The presence of up to 54% PMMA homopolymer in PCL-PMMA block copolymer did not prevent the formation of such pitted morphology on the surface. The effect of the chemical structure of the second block and the possible orientations of the block copolymer molecules in thin films are discussed.
The AFM Observation of Single Polyethylene Molecules in Coiled State on Mica
AIP Conference Proceedings, 2003
Single polyethylene molecules and their small aggregates have been deposited on mica from diluted solutions at elevated temperatures and visualized by AFM in coiled and crystalline states. Coils have two-dimensional conformations with both highly tangled sites and locally extended segments with a length much exceeding the persistent length in a solution. The length measurements of coils reveal a wide distribution with the length of a maximum much smaller than the length of fully stretched molecules, moreover the long coils have been observed indicating the existence of linear multimolecular aggregates. Two models have been considered for the explanation of the observed deficit in the coils length, correspondingly the model implying the substantial smoothing of a winding chain trajectory due to the lack of the AFM resolution and the model of locally extended surface conformations with the long intramolecular folds. The roots of the apparent negative AFM height contrast of coils have been discussed.
An intriguing morphology in crystallizable block copolymers
Macromolecules, 1993
The complex and important structures formed by assembly of amphiphilic molecules result from a delicate balance between competing intermolecular forces. In the simplest example, soap molecules surround and divide oil droplets in water. In biological systems the intricate function of selective membranes and cellular structures is determined by such forces. The variety of phases formed by polar lipids are notable for their sensitivity to the intermolecular forces dictating their In polymeric systems, the length of the chain molecules exacerbates this balance of forces, often producing new and unique top~logies.~ While the influence of crystallization of one of the components has been known for some time,5 we have discovered that the unique interplay between hydration and ordering can produce new morphologies, namely, cylindrical structures coexisting with spheres and lamellae. These new structures provide a visual display of the intricate balance between ordering and curvature in self-assembling polymers.
Langmuir, 1996
We use atomic force microscopy (AFM) with phase detection imaging (PDI) in order to study the surface microdomain morphology of thick (i.e., ca. 2 mm) films of triblock copolymers. We present here the results obtained on a poly(methyl methacrylate)-block-polybutadiene-block-poly(methyl methacrylate) (PMMAb-PBD-b-PMMA) copolymer prepared by using a 1,3-diisopropenylbenzene (DIB)-based difunctional anionic initiator. Our data illustrate the interest of PDI for the elucidation of surface phase separation in block copolymers. We show that the surface of thick films studied by this new technique exhibits a two-phase structure corresponding to the two types of components.
Investigation of a stimuli-responsive copolymer by atomic force microscopy
Polymer, 2000
The aim of this study was to investigate the stimuli-responsive behaviour of a pH-and temperature sensitive polymer system, i.e. a random copolymer of N-isopropylacrylamide and acrylic acid by atomic force microscopy (AFM). AFM allowed high resolution images of the physical states of the polymer chains at different conditions. Different collapsed and extended chain conformations of a random copolymer were seen over a wide range of pH and temperature. The shapes of both the individual copolymeric chains and globules can be clearly identified. Here we demonstrate the potential of AFM for characterising the stimuli responsive behaviour of such "smart" polymers.
Surface Evolution of Copolymer thin Films as Revealed by Atomic Force Microscopy
MRS Proceedings, 1991
Atomic Force Microscopy has been used to study the early stage evolution of the free surface of annealed symmetric poly(styrene-b-n-butylmethacrylate) diblock copolymer thin films. As the lamellar ordering propagates through the film thickness, Islands or holes are formed on the free surface. It Is shown that, depending on the Initial film thickness, I.e. on the fraction of the film surface occupied by the islands (or holes) In the ordered state, the existence or non-existence of spatial correlations characterizes the ordering kinetics of both islands and holes. However, the limit between these two regimes is not the same in the two cases : in the case of holes, spatial correlations occur for a higher value of the surface coverage than In the case of islands.