Main Project:

Laterally-resolved physical properties using Atomic Force Microscopy (AFM): building a bridge between molecular response and macroscopical properties

Started at:
– Instituto de Estructura de la Materia (IEM-CSIC). Madrid, Spain. (2011-2014. Currently collaborating with the SoftMatPol-SUNLab group)

Continued at:
– Université libre de Bruxelles. Brussels, Belgium. (2012, 2014-2015)
– Donostia International Physics Center & Materials Physics Center. Donostia, Spain. (2016-2018)
– University of the Basque Country (2018 – present)

Main results:

– Study of polymers and soft matter morphology, especially focusing on nanostructured systems. Please refer to publications no. 3,4, 5, 7,8,9,10,11,12, 13,15,16,17,18,22,23

– Dielectric imaging and nanoDielectric Spectroscopy (nDS). Using AFM-based techniques for the study of ionic conductivity in polymer-based systems. For details, please refer to publication no. 19.

-Crystallization of polymers and organic molecules. Please refer to publications no. 10,13,15.

– Mechanical properties by Peak Force Tapping – QNM. Mechanical maps with lateral-resolution of a polymer nanocomposite, gathering information of mechanical modulus, adhesion force, and dissipation energy, simultaneously. For details, please refer to publications no. 8, 23, 25.

– Transport properties of semiconducting polymers, polymer blends, and inorganic surfaces. Conductive AFM (C-AFM) measurements allowed to characterize the transport properties of model semiconducting polymers, such as P3HT, as well as donor-acceptor organic blends. For details, please refer to publications no. 12,16.

– Writing & reading ferroelectric information at the nanoscale by Piezoresponse Force Microscopy (PFM). Here, nanometric sized bits were written onto nanostructured polymer surfaces, using the AFM tip as a *stylus*. Afterward, the data was read by analyzing the piezoelectric response of the sample. For details, please refer to publications no. 3 & 11.

Ongoing Projects:

Exploring the molecular nature of dielectric relaxations and transport properties using high lateral resolution AFM methods.

– Donostia International Physics Center & Materials Physics Center. Donostia, Spain. (2016-2018)
– University of the Basque Country (2018 – present)
Collaborating with the Bayreuth University, Prof. Papastavrou’s group (2018 – present). **Funded by the EUSMI platform**

Main results:

– Study of the ionic conductivity in PEO thin films, using nanoDielectric Spectroscopy. This AFM technique allowed to explore the ionic transport properties at the nanoscale, where we found a conductivity distribution dependent on the sample preparation method and thermal history. We have evidenced the role of the amorphous-crystalline interfaces, at the molecular scale, on the material transport properties.

Currently working on:

– Transport properties of PEO-based electrolytes. See publication no. 19 for more details.
– nDS measurements under controlled humidity conditions.
– nDS study of PEO-based “all polymeric” blends.

Nanoscale imaging of polymeric unimolecular objects by AFM: improving resolution by mechanical contrast.

– Donostia International Physics Center & Materials Physics Center. Donostia, Spain. (2017-2018)
– University of the Basque Country. (2018 – present)

Main results:

-Study of soft-nanocomposites: single-chain nanoparticles (SCNP) embedded into a polymer matrix: Dependence of the SCNP shape as a function of molecular weight and solvent nature.

–  Study of SCNP aggregation when confined into a polymer matrix.

– Study of the morphological limits of miscibility in SCNP-based blends.

Nanoscale structuring and physical behavior of furan-based polymers.

Collaboration with Dr. Michelina Soccio & Prof. Nadia Lotti at the Dipartimento di Ingegneria Civile, Chimica, Ambientale e dei Materiali (DICAM – Italy). (2017-present). **Funded by the EUSMI platform**

Laser nanostructuring of materials: from processing to understanding the confinement effect on physical properties, as evaluated by AFM.

Collaboration with Dr. E. Rebollar,  LANAMAP group. Instituto de Química Física Rocasolano (IQFR-CSIC). Madrid, Spain. (2013-present)

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Previous Projects & Collaborations

– Nanomechanical properties of hybrid latex films.

Collaboration with Elodie Limousin and Prof. J. M. Asua. POLYMAT. Donostia – Spain. (2018 – 2019). See publication no. 25 for more details.

– Molecular dynamics of topologically complex cyclic polymers.

– Donostia International Physics Center & Materials Physics Center. Donostia, Spain. (2018)

Main results:

– Use of broadband dielectric spectroscopy as a fundamental tool for the determination of cyclic purity. Using regioregular linear chains, it was possible to observe the end-to-end vector fluctuations and their disappearance when a cycle was synthesized.

– Study of “2-arms” polymers with complex dipolar microstructure, using broadband dielectric spectroscopy.

– Broadband Dielectric Spectroscopy of conducting nanocomposites.

Universidad Simón Bolívar (USB). Caracas-Venezuela. (2010)

Main results:

The conductivity and transport mechanism of a poly(lactic acid) + multiwalled carbon nanotubes were studied by Broadband Dielectric Spectroscopy. The influence of the polymer matrix crystallinity on the transport properties was evaluated. For details, please refer to publication no. 2.

– Development and adaptation of physicochemical protocols for a top-down approximation onto the preparation of polymer nanospheres.

Instituto de Estructura de la Materia (IEM-CSIC). Madrid, Spain. (2011-2014)

Main results:

Departing from commercially available products it was possible to prepare polymer nanospheres with a high-efficiency throughput and no presence of contaminants. Controlling and adapting the techniques allowed to span a wide range of diameter, from 10 to 100 nm. The attached image shows a distribution of polystyrene nanospheres prepared by a miniemulsion technique, as observed by Atomic Force Microscopy (AFM). More details on this project can be found at publications number: 4, 7, 9.

– Glass transition temperature variations of polymer nanospheres.

Instituto de Estructura de la Materia (IEM-CSIC). Madrid, Spain. (2011-2014)

Main results:

By Differential Scanning Calorimetry (DSC) the glass transition temperature (Tg) of polymer nanospheres was measured. Model systems made from polystyrene (PS), poly(ethyl methacrylate) (PEMA) and poly(bisphenol A carbonate) (PBAC) were used. We found that, systematically, the Tg of the polymer nanospheres showed a higher value in comparison to their bulk counterparts. We proposed a model based on the number of repeating units englobed onto each nanosphere, to account for these variations. For details, please refer to publications no. 4 & 7.

– Non-volatile organic memories: Writing and reading bits of information at the nanoscale.

Instituto de Estructura de la Materia (IEM-CSIC). Madrid, Spain. (2012-2014)

Main results:

The project was divided into two parts.

(1) Assessing the creation of functional ferroelectric nanostructures.

In collaboration with the “Instituto de Microelectrónica de Barcelona (CSIC), Barcelona-Spain”, we prepared a nanostructured thin film of the ferroelectric copolymer poly(vinylidene fluoride-co-trifluoro ethylene) P(VDF-TrFE). On this film, the nanostructures were created by the hot embossing Nanoimprint Lithography (NIL) technique. Later on, we modified our approach in order to create the nanostructures by a non-contact pulsed laser technique, in collaboration with the “Instituto de Química Física Rocasolano (IQFR, CSIC), Madrid-Spain”. Although the P(VDF-TrFE) is not a suitable candidate for laser nanostructuring, we overcame the problem by preparing a thin film polymer bilayer.

(2) Writing and reading information.

In order to test the nanostructures, we performed Piezoresponse Force Microscopy measurements (PFM). In this AFM-based technique, we were able to write dots of information by applying a DC bias. 0 and 1s were determined by the sign of the applied voltage. Reading of the bits was attained by the evaluation of the piezoelectric effect at the different poled areas. Our nanostructured materials showed an information density of about 0.5 Tbit/inch2.

– Confinement effects on poly(L-lactide) ultrathin films.

Université libre de Bruxelles (ULB). Brussels, Belgium. (2012, 2014-2015)
Instituto de Estructura de la Materia (IEM-CSIC). Madrid, Spain. (2014)
KU Leuven. Leuven, Belgium. (2012)

Main results:

Using the poly(L-lactide) (PLLA) as a model system, we investigated the deviation on its dynamics when confined to ultra-thin films. Broadband dielectric spectroscopy, AFM and ellipsometry allowed us to obtain a broad description of the system. The semi-crystalline nature of the PLLA allowed understanding how the constraints imposed by crystallization alter the dynamics under confinement. For further details, please refer to publications no. 6 & 10.

An AFM image of a PLLA crystal can be found here.

 – Preparation of polymer-based nanoparticles by pulsed laser ablation in liquids (PLAL)

Instituto de Química Física Rocasolano (IQFR-CSIC). Madrid, Spain. (2013-2014)
Collaboration with Dr. E. Rebollar,  LANAMAP group.

Main results:

Polymer-based nanoparticles were prepared by irradiation of a poly(bisphenol A carbonate) (PBAC) target, using a pulsed laser in the ultraviolet region. The PBAC target was immersed in different liquids. We found that depending on the physicochemical characteristics of each liquid, nanoparticles of different morphologies were formed.

From the results found in this project, it was possible to develop PLAL based techniques for the preparation of complex polymer nanocomposites, for example, the inclusion of metallic nanoparticles onto polymer matrices. Further details concerning this project can be found at publication no. 18.

– Laser Induced Periodic Surface Structures (LIPSS): New problems and ideas.

Instituto de Química Física Rocasolano (IQFR-CSIC). Madrid, Spain. (2014)
Collaboration with Dr. E. Rebollar,  LANAMAP group.

Main results:

Periodic nanostructures were prepared on the ferroelectric copolymer P(VDF-TrFE). In order to overcome the low light absorption coefficient of this material, a bilayer approach was used. We demonstrated the possibility of forming nanostructured functional surfaces with this approach. For further details, please refer to publication no. 11.

We further explored the formation of LIPSS by playing with the irradiation parameters. For example, we have explored the possibility of nanostructure formation when the laser beam is passed through cross polarizers.

– Pulsed Laser Deposition of Aluminum films.

Instituto de Química Física Rocasolano (IQFR-CSIC). Madrid, Spain. (2013-2014)
Collaboration with Dr. E. Rebollar,  LANAMAP group.

Main results:

Aluminum thin films were deposited on glass surfaces by Pulsed Laser Ablation Deposition (PLD). By playing with the laser fluence, we managed to obtain aluminum oxide or metallic aluminum deposits. Electrical measurements allowed to determine the conductivity of the deposited films. C-AFM measurements gave further information on the transport mechanisms of the thin films. For more details please refer to publication no. 15.

– Crystallization and confinement induced polymorphisms of organic semiconducting crystals.

Univeristé libre de Bruxelles (ULB). Brussels, Belgium. (2014-2015)
Collaboration with the Chemistry Department of the ULB, and with Dr. Gabin Gbabode at Univesité Rouen (France).

Main results:

Molecules with a benzothiophene (BTBT) core were synthesized by Prof. Geerts group at the ULB Chemistry Department. Using these materials, we studied the formation of crystalline polymorphisms when the molecules were prepared in confined geometries. Different problems were explored, where the structural studies were carried out using a combination of Optical Microscopy, AFM and specular X-Ray diffraction. For example, we studied the diffusion and crystallization of a BTBT molecule immersed onto a polystyrene matrix. The influence of the PS surface onto the crystalline evolution of the BTBT molecule was probed. These results are presented in detail in publication no. 13.

Also, we were able to study the formation of organic nanoplates, made from a fluorinated BTBT molecule. We observed the formation of hexagonal shaped nanostructures, which evolved toward perfect equilateral triangles. This curious geometry was understood when considering the possible crystalline phase transitions suffered by the molecule as its interaction with the supporting substrate was enhanced. Please refer to publication no. 14.

AFM images of BTBT crystals can be found here.

– Characterization of organic molecules grafted onto different surfaces by AFM and ellipsometry techniques.

Collaboration with Dr. Ludovic Troian-Gautier at Université libre de Bruxelles. (2015)

Main results:

Dr. Trojan-Gautier’s developed a chemistry protocol to graft organic molecules onto metallic and polymer surfaces. Our input consisted in characterizing the thickness and morphology of the grafted layers by AFM and ellipsometry. This collaboration lead to the publication of paper no. 17.

– Dielectric relaxation study of a furan-based polymer.

Collaboration with Dr. Michelina Soccio at the Dipartimento di Ingegneria Civile, Chimica, Ambientale e dei Materiali (DICAM – Italy). (2016-2017).

Main results:

Using broadband dielectric spectroscopy (BDS), we have characterized the molecular dynamics of poly(butylene furanoate). This green polymer was studied in its amorphous state until cold crystallization took place. Then, the semicrystalline material was also characterized, where the remaining amorphous phase was deconvoluted into a set of different fractions. This collaboration led to the publication of paper no. 20.

– Advanced synthesis of PEDOT:PSS using Single Chain Nanoparticles.

Collaboration with Prof. J. Pomposo.

Materials Physics Center. Donostia, Spain. (2016-present)

Main result: Synthesis and characterization of PEDOT:PSS complexes, synthesized following a novel preparation route involving the use of single-chain nanoparticles. This collaboration led to the publication of paper no. 22.