@conference{
author = "Stefanović, Ivan and Džunuzović, Jasna and Džunuzović, Enis and Ranđelović, Danijela",
year = "2024",
abstract = "Polyurethane networks (PUNs) are versatile materials that have a wide range of
applications. Their structure is often segmented which means that it is built from thermodynamically incompatible flexible soft (SS) and rigid hard segments (HS) leading to the formation of microphase separation in the PUNs. With the careful design and selection of SS and HS it’s possible to control PUNs structure, morphology, solvent resistance, etc. Here, polycaprolactone (PCL) was used as SS to prepare segmented PUNs, due to its attractive features, such as low glass transition temperature (around -60 °C), biocompatibility, biodegradability, hydrophobicity, good solubility in various solvents, high permeability to many gasses, etc., in order to prepare PUNs with desired surface properties for their application as coatings [1,2].
In this study, a series of PUNs was synthesized by a two-step polymerization process, according to the procedure described elsewhere [1,3]. The synthesized PUNs are based on Boltorn®
hydroxy-functional aliphatic hyperbranched polyester of the second pseudo generation (BH-20,
Mn = 1340 g mol-1), isophorone diisocyanate (IPDI) and polycaprolactone diol (PCL, Mn
= 2000 g mol-1). Five samples with diferent SS content (from 10 to 50 wt.% SS content) and constant –NCO/−OH molar ratio of 1.05 were synthesized. Stannous octoate (Sn(Oct)2
) was used as a catalyst, while a mixture of N,N-dimethylacetamide (DMAc) and tetrahydrofuran (THF) was used as a solvents during the synthesis of PUNs. PUN samples were labeled as PUN-XX, where XX represents the SS content (from 10 to 50). Surface morphology and the surface roughness of the PUNs were investigated by atomic force microscopy (AFM). AFM examination of
PUNs was performed by applying NTEGRA Prima atomic force microscope (NT-MDT, Moscow, Russia). Measurements were done using NT-MDT NSGO1 silicon cantilevers (N-type,
antimony doped with Au reflective coating). The nominal force constant of the cantilevers was
5.1 N m-1, whereas the cantilever driving frequency was around 150 kHz. Intermittent-contact
AFM mode was applied and data related with topography and phase were collected. AFM
images were created and analyzed with Image Analysis 2.2.0 (NT-MDT) and Gwyddion 2.61
(Free and Open Source software, Czech Metrology Institute) software. The scan area of the
PUNs surface was 20 × 20 μm2.
AFM analysis was carried out to explore the surface topography, homogeneity and the
impact of the SS content on microstructural features of the synthesized PUNs, such as nanometer scale structures and roughness. The recorded 3D height and 2D phase pictures (scan size 20
× 20 μm2) and obtained roughness values are presented in Figure 1 and Table 1, respectively.
According to the captured 3D height pictures it can be seen that surface topography of PUNs
strongly depends on the SS content. That is reflected in the fact that samples with smaller SS
content have more flat and smoother relief structures, without any larger domains, opposite
to the samples with the higher SS content. Furthermore, according to the presented 2D phase
pictures it can be observed that prepared PUNs have heterogeneous surface morphology, due to
the existence of more pronounced and more noticeable interface borders between phases. This
behavior is more prevalent in PUN samples with higher SS content [3]. The examined roughness of the PUNs shows that samples with SS content of 30 and 40 wt.% (PUN-30 and PUN-40
samples) have the highest roughness values (Rq and Ra, Table 1). The reason for this may lie in the fact that these samples have optimal ratio between HS and SS, allowing easier organization of SS [4].
A series of PUNs based on BH-20, IPDI and PCL was successfully synthesized. AFM
analysis showed that the content of SS has a significant impact on the surface properties of
these PUNs. Moreover, PUNs have two phase morphology that originates from the presence of
HS and SS, and it was more pronounced in the samples with higher SS content [5].
.",
publisher = "Serbian Academy of Sciences and Arts",
journal = "Third International Conference On Electron Microscopy Of Nanostructures (ELMINA 2024), Program and Book of Abstracts; September 9-13, 2024, Belgrade, Serbia",
title = "Morphology of the Polyurethane Networks Based on Polycaprolactone",
pages = "150-152",
url = "https://hdl.handle.net/21.15107/rcub_cer_7839"
}
