placing polystyrene (ps) beads onto the pva-coated surface

Exploración de sistemas poliméricos multifásicos mediante espectroscopía infrarroja a nanoescala

Atomic force microscopy (AFM) has become essential to image and characterize the morphology of a wide variety of samples with nanoscale resolution1,2,3. By measuring the deflection of an AFM cantilever resulting from the interaction of the sharp tip with the sample surface, nanoscale functional imaging protocols for local stiffness measurements and tip-sample adhesion have been developed4,5. For soft condensed matter and polymer analysis, AFM measurements exploring the nanomechanical and nanochemical properties of local domains are highly sought after6,7,8. Before the emergence of nanoscale infrared (nanoIR) spectroscopy, AFM tips were chemically modified to assess the presence of different domains from the AFM force curve and deduct the nature of the tip-sample interaction. For instance, this approach was used to unveil the transformation of microdomains of poly(tert-butyl acrylate) at the surface of cyclohexane-treated polystyrene-block-poly(tert-butyl acrylate)block copolymer thin films at the sub 50 nm level9.
The combination of infrared (IR) light with AFM has had a significant impact on the field of polymer science6. Conventional IR spectroscopy is a widely used technique for studying the chemical structure of polymeric materials10,11, but it fails to provide information on individual phases and interphase behavior, as the regions are too small compared to the size of the IR beam used to probe the sample. The problem holds with IR microspectroscopy, as it is restricted by the optical diffraction limit6. Such measurements average the contributions of the entire region excited by the IR light; the signals resulting from the presence of nanoscale phases inside the probed region either exhibit complex fingerprints that should be deconvoluted during post-processing or are lost due to a signal level below the detectable level. Hence, it is essential to develop tools capable of nanoscale spatial resolution and high IR sensitivity to explore nanoscale chemical features in complex media.
Schemes to achieve nanoIR spectroscopy have been developed, first using a metallic AFM tip as a nanoantenna12,13, and more recently exploiting the AFM cantilever&#39;s ability to monitor changes in the photothermal expansion incurred during IR illumination of the sample12,14,15. The latter uses a pulsed, tunable IR light source tuned to an absorption band of the material probed, which causes the sample to absorb radiation and undergo photothermal expansion. This approach is well-suited for organic and polymeric materials. The pulsed excitation makes the effect detectable by the AFM cantilever in contact with the sample surface in the form of an oscillation. The amplitude of one of the contact resonances of the system observed in the frequency spectrum is then monitored as a function of illumination wavelength, which constitutes the nanoIR absorption spectrum of the material beneath the AFM tip15. The spatial resolution of nanoIR imaging and spectroscopy is limited by various effects of the photothermal expansion of the material. It has been evaluated that photothermal nanoIR spectroscopy using contact mode AFM can acquire the vibrational absorption spectra properties of materials with sub 50 nm scale spatial resolution14, with recent work demonstrating the detection of monomers and dimers of &#945;-synuclein16,17. However, quantitative studies of the performance of nanoIR measurements on heterogeneous polymeric materials assembled in various configurations, such as the case of absorbers of finite dimensions embedded in the volume of various polymeric films, remain limited.
This article aims to create a polymeric assembly with an embedded feature of a known dimension to evaluate the sensitivity of photothermal expansion and spatial resolution of nanoIR during surface analysis. The protocol covers the preparation of a polyvinyl alcohol (PVA) polymer thin film on a silicon substrate and the placement of a three-dimensional polystyrene (PS) bead onto or embedded in the PVA film, which constitutes the formation of the model system. NanoIR imaging and spectroscopy measurements are described in the context of evaluating the signals generated by the same PS bead positioned on or beneath the PVA film. The influence of the bead position on the nanoIR signals is evaluated. Methods to assess the spatial footprint of the bead in the nanoIR map are discussed, and the effects of several parameters are considered.

Autor destacado: Avances en espectroscopia infrarroja a nanoescala para explorar sistemas poliméricos multifásicos  

Avances en espectroscopía infrarroja a nanoescala para explorar sistemas poliméricos multifásicos

Watch this Scientific Journal Video about Placing Polystyrene PS Beads onto the PVA-Coated Surface at JoVE.com

Placing Polystyrene (PS) Beads onto the PVA-Coated Surface  

Colocación de perlas de poliestireno (PS) en la superficie recubierta de PVA

Para empezar, limpia un sustrato de silicona con alcohol isopropílico y déjalo secar al aire. Con una pipeta, coloque un microlitro de perlas de poliestireno suspendidas en agua en el centro del sustrato. Coloque el sustrato agregado con perlas de poliestireno en un compartimento de almacenamiento que contenga desecante de arcilla bentonita para permitir que el agua se evapore.Examine el sustrato de perlas de poliestireno seco y un sustrato recubierto de alcohol polivinílico o PVA previamente preparado bajo un microscopio óptico. Con unas pinzas ultrafinas, pierda suavemente las cuentas, luego recoja algunas cuentas con un pincel de pelo fino y golpee suavemente los pelos del pincel sobre la oblea recién recubierta de PVA. Repita la recolección de las perlas hasta que las perlas individuales de poliestireno se adhieran a la superficie del PVA, según lo confirmado por microscopía óptica.La deposición de las perlas de poliestireno se confirmó mediante microscopía electrónica de barrido de la perla de cinco micrómetros sobre un sustrato de silicio prístino sobre una película de PVA y cubierta con PVA.

placing-polystyrene-ps-beads-onto-the-pva-coated-surface

Research

JoVE Journal

Engineering

Placing Polystyrene (PS) Beads onto the PVA-Coated Surface

99 vistas. Para empezar, limpia un sustrato de silicona con alcohol isopropílico y déjalo secar al aire. Con una pipeta, coloque un microlitro de perlas de poliestireno suspendidas en agua en el centro del sustrato. Coloque el sustrato agregado con perlas de poliestireno en un compartimento de almacenamiento que contenga desecante de arcilla bentonita para permitir que el agua se evapore.Examine el sustrato de perlas de poliestireno seco y un sustrato recubierto de alcohol polivinílico o PVA p...

Video: Placing Polystyrene (PS) Beads onto the PVA-Coated Surface  

Advances in Nanoscale Infrared Spectroscopy to Explore Multiphase Polymeric Systems

Multiphase polymeric systems encompass local domains with dimensions that can vary from a few tens of nanometers to several micrometers. Their composition is commonly assessed using infrared spectroscopy, which provides an average fingerprint of the various materials contained in the volume probed. However, this approach does not offer any details on the arrangement of the phases in the material. Interfacial regions between two polymeric phases, often in the nanoscale range, are also challenging to access. Photothermal nanoscale infrared spectroscopy monitors the local response of materials excited by infrared light with the sensitive probe of an atomic force microscope (AFM). While the technique is suitable for interrogating small features, such as individual proteins on pristine gold surfaces, the characterization of three-dimensional multicomponent materials is more elusive. This is due to a relatively large volume of material undergoing photothermal expansion, defined by the laser focalization onto the sample and by the thermal properties of the polymeric constituents, compared to the nanoscale region probed by the AFM tip. Using a polystyrene (PS) bead and a polyvinyl alcohol (PVA) film, we evaluate the spatial footprint of photothermal nanoscale infrared spectroscopy for surface analysis as a function of the position of PS in the PVA film. The effect of the feature position on the nanoscale infrared images is investigated, and spectra are acquired. Some perspectives on the future advances in the field of photothermal nanoscale infrared spectroscopy are provided, considering the characterization of complex systems with embedded polymeric structures.

This protocol describes the application of atomic force microscopy and nanoscale infrared spectroscopy to evaluate the performance of photothermal nanoscale infrared spectroscopy in the characterization of three-dimensional multi-polymeric samples.

Multiphase polymeric systems encompass local domains with dimensions that can vary from a few tens of nanometers to several micrometers. Their composition ...