Phenyl-methyl phosphazene derivatives for preparation and modification of hydrophobic properties of polymeric nonwoven textiles

Article abstract of DOI:10.1016/j.reactfunctpolym.2015.12.013

This paper focuses on the preparation of two types of hydrophobic nanolayers using electrospinning technology. The first synthetic approach consists in direct fiberizing of polymeric phenyl-methyl-polyphosphazene Ph-Me(p) with the aim to preparing nanolay

Full text of DOI:10.1016/j.reactfunctpolym.2015.12.013

Reactive and Functional Polymers 100 (2016) 53–63
Contents lists available at ScienceDirect
Reactive and Functional Polymers
journal homepage: www.elsevier.com/locate/react
Phenyl-methyl phosphazene derivatives for preparation and
modification of hydrophobic properties of polymeric nonwoven textiles
b
c
a
d
c
Radka Bačovská a, , Patty Wissian-Neilson , Milan Alberti , Jiří Příhoda , Lucie Zárybnická , Zbyněk Voráč
⁎
a
Department of Chemistry, Faculty of Science, Masaryk University, Kotlářská 267/2, 611 37, Brno, Czech Republic
Department of Chemistry, Southern Methodist University, Dallas, 75275-031, TX, US
Department of Physical Electronics, Faculty of Science, Masaryk University, Kotlářská 267/2, 611 37, Brno, Czech Republic
Institute of Chemistry and Technology of Macromolecular Materials, Faculty of Chemical Technology, University of Pardubice, Studentská 573, 532 10, Pardubice, Czech Republic
b
c
d
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 31 May 2015
Received in revised form 17 December 2015
Accepted 29 December 2015
Available online 31 December 2015
This paper focuses on the preparation of two types of hydrophobic nanolayers using electrospinning technology.
The first synthetic approach consists in direct fiberizing of polymeric phenyl-methyl-polyphosphazene
Ph-Me(p) with the aim to preparing nanolayers that have significant hydrophobicity and thermal stability. The
preparation of Ph-Me(p) is a multi-step reaction which produces a relatively low amount of the product. The sec-
ond area of our interest was the creation of nanofibers formed from a mixture of some commercially available
organic polymers and a cyclo-phosphazene derivative. In this case, tri(phenyl)-trimethyl-cyclo-triphosphazene,
Ph-Me(t), whose synthesis is less complicated than its polymeric form, was used as an additive. The influence
of the Ph-Me(t) additive in the nanofibers on the affinity to water was compared with the affinity of nanolayers
made from a pure commercial polymer, i.e. without any phosphazene additive. It was also shown that the hydro-
phobic properties of fibers formed from Ph-Me(p) dissolved especially in THF are better than those of the nano-
fibers composed of a commercial polymer with the addition of Ph-Me(t).
Keywords:
Polymeric nanofibers
Electrospinning technology
hydrophobicity
Ph-Me (t) additive
Ph-Me (p) polyphosphazene
© 2016 Elsevier B.V. All rights reserved.
1. Introduction
well as the hydrophobic character of the whole modified polymer. The
mixture, containing a polymer and an additive, can be further shaped
There are many researchers who concentrate on the functionalization
of nanofiber layers. However, this modifying process, influenced by
the structure of the respective polymer, leads to newly created
bonds that could modify significantly the properties of the final
product [1]. It is usually expected that any additive to a polymer
can preserve the polymer's original chemical structure wherein cer-
tain physical properties (such as hydrophobicity) of the modified
polymer can be changed. [2].
It can be also expected that the original properties of a polymer and
those of the additive merge into more suitable properties of the
resulting material. A common cyclo-phosphazene derivative, containing
non-polar organic side groups, could significantly increase the hydro-
phobic character of the whole cyclo-phosphazene molecule [10] as
by various processing techniques, e.g. electrospinning, which is widely
used for producing polymer nanofibers.
The following phosphazene compounds – trimeric tri(phenyl)-
trimethyl-cyclo-triphosphazene, Ph-Me(t) (used as an additive), and
polymeric phenyl-methyl-polyphosphazene, Ph-Me(p) – were synthe-
sized according to the methods proposed by Patty Wisian-Neilson [3,4]
(Schemes 1 and 2).
The electrospinning technology, which was used in the fiberizing
process, is based on the creation of fibers in a high electrostatic field.
The nanofibers are created from the surface of a polymer solution (or
from its melt) placed on the top of the static powered rod. When the
electrical field reaches its critical value, nanofibers are ejected from
the positively-charged rod electrode towards the grounded negative
electrode, called the collector. The solvent evaporates during this pro-
cess and nanofibers are deposited on the supporting textile material,
e.g. polypropylene foil (PP band), that the collector is covered with.
[5–9] Fig.1 shows the scheme of the electrospinning device.
Nanotextiles, made commonly by electrospinning from commer-
cial polymers, can be modified either by addition of the simple
phosphazene Ph-Me(t), or they can be made directly from its polymeric
form, i.e. Ph-Me(p). The polymeric nanolayers should exhibit, due to a
higher number of organic –CH, –CF3 groups and thin fibers, a relatively
high hydrophobicity.
Abbreviations: Ph-Me(t), tri(phenyl)-trimethyl-cyclo-triphosphazene; Ph-Me(p),
phenyl-methyl-polyphosphazene; PA6, polyamide 6; PS, polystyrene; ASA, acrylonitrile-
styrene-acrylate; SAN, styrene- acrylonitrile; PESU, polyethersulphone; PP, polypropyl-
ene; THF, tetrahydrofurane; TFA, trifluoroacetic acid; DMS, dimethyl sulfide; AFA, mixture
of acetic and formic acids; Tad, minimum thermal decomposition temperature; TGA, ther-
mogravimetric analysis; SEE-system, Surface Energy Evalution system analysis; SEM, scan-
ning electron microscope; EDX, X-ray photo-electron spectroscopy; ATR-FTIR, attenuated
total reflectance Fourier transform infra-red; NMR, nuclear magnetic resonance.
⁎
Corresponding author.
E-mail address: radkabacovska@centrum.cz (R. Bačovská).
http://dx.doi.org/10.1016/j.reactfunctpolym.2015.12.013
1381-5148/© 2016 Elsevier B.V. All rights reserved.

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R. Bačovská et al. / Reactive and Functional Polymers 100 (2016) 53–63
Scheme 1. Synthesis of Ph-Me(t).
Scheme 2. Synthesis of Ph-Me(p).
The resulting nanolayers can be manually removed from the sup-
porting textile and used, e.g. as a protective material.
nanofibers were created only from a single polymer or copolymer
(Fibers 1). The second part of the samples was mixed with Ph-
Me(t) (as an additive) (see Table 1). The content of Ph-Me(t) was either
one or ten weight per cent related to the whole commercial polymer
contained in the fiberized mixture. It follows from preliminary
experiments that a 10 wt.% concentration of Ph-Me(t) is optimal for suf-
ficient modification of fibers (Table 1). Therefore, more space in this
article is devoted to fibers containing ten weight per cent of the Ph-
Me(t) additive in the fiberized mixture.
2. Experimental
2.1. The preparation of solution for electrospinning
Nanofibers were made from two different solutions, which differ in
their composition.
The solutions were manually homogenized for 1 h using an electro-
magnetic stirrer before electrospinning.
▪ The commercial polymers – Polystyrene (PS), Polyamide 6 (PA6) or
Polyethersulphone (PESU) – or copolymers – acrylonitrile-styrene-
acrylate (ASA) or styrene-acrylonitrile (SAN) – were fiberized on
their own (Fibers 1) and with Ph-Me(t) as an additive (Fibers 2).
▪ Ph-Me(p) was fiberized on its own (Fibers 3).
The properties of all the resulting types of nanofibers were com-
pared with each other.
2.1.1. Solutions of commercial organic polymers with and without Ph-
Me(t) as additive (Fibers 1, 2) and creation nanofibers from these solutions
The commercial polymers (PA6, PS, ASA, SAN, PESU) were produced
by BASF, the solvents were delivered by Sigma Aldrich.
The above mentioned polymers were first dissolved in one of the
following diluents — trifluoroacetic acid (TFA), a mixture of acetic and
formic acids (AFA) or dimethylformamide (DMF). The prepared solu-
tions of polymers were, for the following experiments, divided into
two parts. The first part of the samples was fiberized on its own, i.e.
Fig. 1. Scheme of the electrospinning apparatus.

R. Bačovská et al. / Reactive and Functional Polymers 100 (2016) 53–63
55
Table 1
The composition of fiberizing solution and electrospinning characteristic.
2.1.2. Solution of Ph-Me(p) (Fibers 3)
The solution of Ph-Me(p) in a 25 wt.% concentration was prepared in
THF or TFA (see Table 1). This solution served as a source for creating
nanofibers.
Polymer
Solvent
Concentration ratios (wt.%)
Ph-Me(t)
Organic polymer
Solvent
PA6
PS
ASA
SAN
PESU
Ph-Me(p)
TFA, AFA
DMF
DMF
DMF
DMF
1.19
2.44
2.44
2.44
1.96
without
11.86
24.39
24.39
24.39
19.61
25.0
86.96
73.17
73.17
73.17
78.43
75.0
2.2. Nanolayer analysis
The chemical composition of nanofibers was determined by physi-
cochemical methods. The presence of the phosphazene additive,
Ph-Me(t), in the fiber layers was confirmed by the ATR-FTIR and 31P
NMR spectroscopies. The elemental composition of fibers, made from
Ph-Me(p), was confirmed by the EDX, ATR-FTIR analyses and also by
31P NMR spectroscopy. The macroscopic structure of the fibers was
investigated using the SEM technology and their hydrophobicity was
determined using the SEE system analysis. The thermal stability of
nanofibers was investigated by TGA analysis.
THF, TFA
Nanofibers were formed from the powered rod electrode (see Fig. 1)
using the Elmarco Nanospider™ NSLAB 500 pilot plant unit. Polypropyl-
ene foil (PP foil) was used as the supporting material covering the
grounded electrode. In the electrospinning process, drops of the poly-
mer solutions were placed on the top of the electrode rod, while all
the drops were approximately the same size. Each drop was later
fiberized for at least 5 min. To create an approximately 50-μm-thick
nanolayer, the deposition process had to be repeated five times. Then,
nanofibers were removed from Nanospider together with the
supporting PP foil and were allowed to dry at 25 °C for 1 h in order for
the rest of the solvent to evaporate. Then the samples were placed in
plastic bags for further analysis.
2.2.1. ATR-FTIR analysis
Attenuated total reflectance Fourier transform infra-red spectra
(ATR-FTIR) were measured by the Brucker Vertex 80 V spectrometer.
The solid samples were measured in attenuation total reflection mode
using a diamond crystal. The sample compartment was evacuated to
2.51 hPa. The spectral range was calibrated from 4000 to 600 cm−1
.
Each spectrum was scanned a hundred times. Bruker OPUS software
was used for spectra evaluation and the baseline correction was done
by “rubber-band”.
The composition of the polymer solutions used is shown in Table 1.
The parameters, such as electrode distance, voltage and current, were
kept at approximately the same level for all samples. The distance be-
tween electrodes was 170 mm, the voltage was 40 kV and the current
was around 0.003 mA.
The characteristic vibration of the phosphazene cycles was observed
about at 1210 cm−1 [10].
Fig. 2. The contact angle for hydrophilic and hydrophobic materials.
Fig. 3. a–e: ATR-FTIR spectra of fibers made from commercial polymers and those made from commercial polymers with Ph-Me(t) as an additive.

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Fig. 4. The SEM nanofibers structures and water drops on the nanofibers.

R. Bačovská et al. / Reactive and Functional Polymers 100 (2016) 53–63
57
2.2.2. 31P NMR spectroscopy
In the spectra of fibers containing Ph-Me(t) and PS, ASA and SAN
(Fig. 3b, c, d), vibrations at around 1200 cm−1, belonging to the
phosphazene cycle, were observed while no vibrations at about the
same wavenumber were found in the pure polymer spectra. In the
case of PA6 and PESU, it was difficult to determine Ph-Me(t) vibrations
(Fig. 3a, e), because the vibrations at around 1200 cm−1, belonging to
Ph-Me(t), overlapped with those of the pure polymers.
To avoid these problems with the identification of bands, the pres-
ence of Ph-Me(t) in the nanofibers had to be confirmed by another
method, e.g. 31P NMR analysis. The nanolayer, prepared from Ph-
Me(t) and a commercial polymer/copolymer, was peeled from the PP
supporting foil, dissolved in THF or TFA and measured. The 31P chemical
shift of the Ph-Me(t) extracted from the nanolayer was observed as a
singlet at around 18.8 ppm in the spectra. This is in agreement with
the value of chemical shift for Ph-Me(t) (δ = 19.0 ppm) synthesized
by standard methods [13]. A small split in the signal can be ascribed to
the influence of hydrogen atoms from the Ph and Me groups.
The microscopic structure of the nanofiber layers was studied using
the SEM technique (Fig. 4).
It follows from the SEM snaps that fibers formed from the PA6, PS
and SAN matrix materials are spread relatively homogenously, with
just a few irregularities. No fiber orientation is observed there. The fibers
made from ASA and PESU do not create homogenous layers. It follows
from Fig. 4 that the ASA and PESU samples show the possibility of com-
bination of electrospinning and electrospraying (i.e. the creation of
drops instead of fibers). In this case, these drops create centers for fur-
ther formation of shorter daughter-fibers. These daughter-fibers are rel-
atively thin and inhomogeneous.
The behavior of water drops, being in contact with a nanolayer sur-
face, was tested using the SEE system analysis (the water drops on the
nanolayer surface are depicted as small pictures in the corners of Fig. 4
for each sample separately).
31P NMR spectra were measured in solutions of dissolved nanotextile.
The spectra were recorded using a BRUKER AVANCE DRX 300 instru-
ment at the frequency of 202.46 MHz, 85% solution of H3PO4 was used
as the external standard. The samples were sealed in Simax tubes
(4 mm in diameter), inserted in NMR cuvettes (5 mm in diameter) filled
with D2O (external lock). The spectra were measured in the coaxial NMR
cuvette system.
2.2.3. SEM analysis with EDX detector
The images of the nanofibers were made using the Tescan MIRA3
scanning electron microscope (SEM) equipped with energy X-ray dis-
persive (EDX) analyzer. The nanolayer was fitted onto the pad using a
sticky tape and its surface was covered by a 30 nm gold layer. The sam-
ples were measured using the secondary emission mode, the depth
regime of 15 kV, the working distance (WD) of 10 mm and 20,000×
magnification. Contrast-enhancing coloring was used for contrast visu-
alization. The fiber size was determined using ImageJ software with
manually located fiber borders. [11] The surface elemental analysis
was determined by Energy Dispersive X-ray Spectroscopy (EDX) (Oxford
Instruments) and evaluated by Aztec 2.1a software.
2.2.4. Surface energy evaluation system analysis (SEE system analysis)
The contact angle between the free surface of nanolayers and the
water drop characterizes the extent of hydrophobicity. [12] Constant
volumes of distilled water were dropped on the nanolayer surface
lying on the microscope pad. Photos of water drops were made, the con-
tact places between the drop and the supporting textile were manually
marked and the contact angle was determined (Fig. 2).
The SEE system results were evaluated using Software 7.0.
2.2.5. Thermogravimetric analysis (TGA)
Table 2 lists the values of the contact angles for fibers containing
only polymers/copolymers (i.e. 0 wt.% of the Ph-Me(t) additive) and
polymers/copolymers with the Ph-Me(t) additive (1 wt.% and 10 wt.%).
The influence of the presence of Ph-Me(t) on the average fiber width
was also investigated. The individual values of fiber width and the
values of contact angles are shown in Table 2.
Thermogravimetric analysis (TGA) was carried out using a TA Instru-
ments TGA Q500. The samples of nanofibers, about 1.350 mg, were
investigated at heating rate 10.0 °C/min, in the temperature range
20–1000.0 °C. The air was used as a purge gas at the flow rate of
60.0 ml/min. The minimum thermal decomposition temperature (Tad)
was determined.
The increase (↑)/decrease (↓) of the fiber width (mentioned as how
many times bigger/smaller the fiber width is) comparing the fibers con-
taining only commercial polymer (Fibers 1) with fibers containing poly-
mer and 10 wt.% of Ph-Me(t) (Fibers 2) is listed in Table 3.
3. Results and discussion
Three types of nanofibers were prepared:
▪ Fibers made from additiveless polymer/copolymer (Fibers 1) and
fibers made from polymer/copolymer with Ph-Me(t) as additive
(Fibers 2) (see Chapter 3.1.).
Table 3
▪ Fibers made from Ph-Me(p) (Fibers 3) (see Chapter 3.2).
The comparison of the value of contact angle and fiber width for 10 wt.% concentration of
Ph-Me(t).
Fiber composition and characteristics
3.1. Fibers made from organic polymer/copolymer with and without Ph-
Me(t) as an additive (Fibers 1, 2)
Fiber composition
Mean fiber width value
Average contact angle
PA6
0.25 nm
0.11 μm
↑440×
4.19 μm
1.44 μm
↓2.91×
0.61 μm
118.55 nm
↓5.16×
0.45 μm
0.06 μm
↓7.50×
22.7°
31.3°
PA6 + Ph-Me(t)
*
PS
PS + Ph-Me(t)
*
ASA
ASA + Ph-Me(t)
*
SAN
SAN + Ph-Me(t)
*
PESU
PESU + Ph-Me(t)
*
ATR-FTIR analysis was performed for both types of nanofibers
(Fig. 3).
37.88%
119.9°
122.9°
2.50%
110.3°
112.7°
2.18%
68.3°
89.7°
31.33%
93.0°
97.1°
4.41%
Table 2
The contact angle value depending on the amount of additive Ph-Me(t).
wt.% of Ph-Me(t)in fibers
0
1
10
Polymer/copolymer
Contact angle (°)
PA6
PS
ASA
SAN
PESU
22.7
23.5
31.3
60.25 nm
0.22 μm
↑3.65×
119.9
110.3
68.3
120.1
111.2
70.4
122.9
112.7
89.7
⁎
The increase (↑)/decrease (↓) of the fiber width the percentage increase of the contact
angle values.
93.0
93.8
97.1

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It follows from Table 3 that the values of contact angles for nanolayers
Ph-Me(p) (with traces of the solvent, which were not evaporated
completely, respectively).
The presence of phosphorus in Ph-Me(p) nanolayers was also con-
firmed using 31P NMR analysis — for polymeric structures typically a
broad signal around the base line with a chemical shift of 1.1 ppm
(Fig. 8) [13].
The appearance of nanofibers is shown by SEM spectroscopy (Fig. 9).
The fiber structure of nanolayers, prepared from THF, is homogenous,
while fibers spun from TFA look a little etched (see the red circles in
Fig. 9). Individual fibers are not distinguishable there.
made from PA6 (22.7°) and PA6 with Ph-Me(t) (31.3°), SAN (68.3°) and
SAN with Ph-Me(t) (89.7°) show slightly hydrophilic properties, while
the contact angles for nanolayers made from PS (119.9°) and PS with
Ph-Me(t) (122.9°), PESU (93.0°) and PESU with Ph-Me(t) (97.1°), ASA
(110.3°) and ASA with Ph-Me(t) (112.7°) show slightly hydrophobic
character.
3.2. Fibers made from Ph-Me(p) (Fiber 3)
The interaction between the nanolayer and water drops was also
studied. Both nanolayers (formed from different solvents) have hydro-
phobic properties as follows from the contact angle values (Fig. 10).
Fibers created from THF are a little bit more hydrophobic (124.1°)
than fibers spun from TFA (114.2°). The width of Ph-Me(p) fibers
created from THF is 1.38 μm and the width of fibers created from
TFA is 0.94 μm.
A similar electrospinning experiment was also carried out with pure
Ph-Me(p). The elemental composition of the resulting polyphosphazene
nanofiber layer was also determined by EDX analysis (Figs. 5, 6A, B). The
ATR-FTIR spectroscopy (Fig. 7) was used for determination Ph-Me(p) in
the nanolayer.
Fig. 5 shows that the distribution of elements contained in Ph-
Me(p) follows the structure of the nanofiber layer. The elemental com-
position of fibers is distinguished in the figure by different colors of
elements.
3.3. Discussion of hydrophobicity
The presence of these elements was also confirmed by the EDX anal-
ysis (Fig. 6A, B). The presence of fluorine and oxygen (Fig. 6B) can be
explained by using fluorinated solvents (TFA) in the course of fiberizing.
It can be easily concluded from above mentioned results that the
fibers are composed only from Ph-Me(p) with residues of solvent.
ATR-FTIR spectra of nanofibers formed from Ph-Me(p) were com-
pared with non-fiberized Ph-Me(p) (Fig. 7). It follows from this figure
that the ATR-FTIR spectra of both compared samples are identical.
Therefore, it can be concluded that this nanolayer is made only from
It follows from the above mentioned results that the formation of
nanofibers from different commercial polymers (PA6, PS, ASA, SAN,
PESU) modified by Ph-Me(t) is possible. The same conclusion can be
claimed also for nanofibers made from polymeric Ph-Me(p) itself.
Fibrous materials themselves exhibit low wettability in comparison
with the same property of a smooth surface of compact pure polymer ma-
trix. It was found that the increased content of Ph-Me(t) in the commer-
cial polymeric fibers (10%) leads to higher hydrophobicity of nanolayers.
Generally, the presence of Ph-Me(t) improves unambiguously the final
Fig. 5. EDX analysis, (nitrogen — green, phosphorus — yellow, carbon — red, and fluorine — light blue). (For interpretation of the references to color in this figure legend, the reader is
referred to the web version of this article.)

R. Bačovská et al. / Reactive and Functional Polymers 100 (2016) 53–63
59
hydrophobic properties of the whole nonwoven material. This also cor-
responds to the fact that surfaces created from extremely thin fibers ex-
hibit better hydrophobicity. The comparison of the values of contact
angles for commercial polymers with and without Ph-Me(t) is shown
in Fig. 11.
With respect to the values of contact angles, we can divide commer-
cial polymers into two basic groups — hydrophilic polymers (PA6, SAN)
and hydrophobic ones (PS, ASA, PESU).
Ph-Me(t), as an additive, leads to the increase of hydrophobic prop-
erties of originally hydrophilic polymers (PA6, SAN) by about thirty
Fig. 6. A: EDX diagrams of Ph-Me(p) nanolayers created from THF B: EDX diagrams of Ph-Me(p) nanolayers created from TFA.

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R. Bačovská et al. / Reactive and Functional Polymers 100 (2016) 53–63
Fig. 7. ATR-FTIR analysis of Ph-Me(p) nanolayer.
percent in contrast to hydrophobic polymers (PS, ASA). Their hydropho-
bicity grows by only about two percent and for PESU polymer around
4%. The above mentioned results also show the significant influence of
the original hydrophobicity of a commercial polymer on the final behav-
ior of the prepared nanolayers. A change in contact angles is more
significant for fibers made from more hydrophilic polymers (i.e. from
PA6, SAN).
The experiments studying hydrophobicity and homogeneity were
carried out using a pure Ph-Me(p) nanolayer, too. Although the size of
the nanofibers created from THF is greater, they are more separated
and they are spread homogenously without any irregularities, in con-
trast with nanofibers created from TFA, which are thinner and not so
homogeneous due to etched places. This is probably caused by a higher
residual amount of TFA in these fiber areas.
Further experiments, in which the influence of Ph-Me(t) as the addi-
tive onto organic polymers/copolymers was studied, were carried out.
Tad values, determined for nanofibers containing only commercial poly-
mer/copolymer (Fibers 1) and for nanofibers with content of Ph-
Me(t) (Fibers 2) are different (see Table 4).
The results in Table 4 show that Tad is significantly decreasing in
case of PA6, ASA, PESU while in case of PS and SAN the difference is
practically negligible. The explanation of this observation can be based
The Ph-Me(p) nanolayer has higher hydrophobicity than layers
created from commercial polymers with Ph-Me(t) as an additive. The
wettability of nanolayer created from Ph-Me(p) dissolved in THF is
worse than the wettability of layer from Ph-Me(p) and TFA.
3.4. Thermal stability of the Ph-Me(t) additive in comparison
with Ph-Me(p)
It is well known that relatively high content of phosphorus and
nitrogen in material leads to the increasing thermal stability [14].
Phosphazene compounds, containing PN groups in the backbone, have
been studied for their thermal stability many times [14,15]. Therefore,
the TGA analysis was carried out to determine the thermal properties
of nanofibers.
The minimum thermal decomposition temperature (Tad) of polymeric
Ph-Me(p) as well as trimer Ph-Me(t) was determined from TGA curves
(see Figs. 12, 13).
The results of TGA analysis confirmed that polymeric Ph-
Me(p) (Tad = 230 °C) decompose at higher temperature than trimer
Ph-Me(t) (Tad = 113,9 °C). This result is rather surprising because the
ratio of P:N in both substances is equal. That means there must be an-
other reason for this difference. The possible explanation could be in
the different structure of phosphazene backbone (cyclic trimer vs. line-
ar polymer). It is highly probable that the thermal decomposition of Ph-
Me(t), with relatively high tension of the cycle, is based on the disinte-
gration of the cycle leading to short linear fragments with reactive cen-
ters, while almost no similar tension of linear polymeric Ph-Me(p) can
be expected. Therefore the thermal decomposition of Ph-Me(p) occurs
at a higher temperature as compared with Ph-Me(t).
Fig. 8. 31P NMR of Ph-Me(p).

R. Bačovská et al. / Reactive and Functional Polymers 100 (2016) 53–63
61
Fig. 9. SEM analysis of nanofibers from Ph-Me(p).
with reactive groups of PA6, SAN, ASA and PESU. Then, such modified
polymers are predisposed to the easier decomposing of polymers/
copolymers backbone which is confirmed by lower Tad. The PS backbone
is relatively unreactive and so the effect of possible reaction between PS
backbone and decomposed Ph-Me(t) is not observed.
4. Conclusion
The phosphazene derivative Ph-Me(t) was used as an additive in
commercial polymers (PA6, PS, SAN, ASA, PESU) to form more hydro-
phobic nanofiber materials created by electrospinning technology. The
polymeric form, Ph-Me(p) especially spun from THF, is an even more
suitable variety for creating layers which are more hydrophobic and
more thermal stable in a comparison with Ph-Me(t). It has been discov-
ered that the presence of the additive Ph-Me(t) can positively increase
the hydrophobicity of organic polymeric fibers, although the hydropho-
bic character of the commercial polymer itself has a greater impact on
the resulting value of the water contact angle.
Fig. 10. SEE system analysis of Ph-Me(p) nanolayers.
on the fact that some polymers bear reactive groups or bonds (PA6–
NH groups, SAN and ASA–CN groups and PESU has oxygen bridge
in the backbone) while PS is relatively unreactive. It is probable that
decomposed Ph-Me(t) in the form of short reactive linear chain, interacts
Fig. 11. The comparison of contact angles values measured on the nanolayer samples (Fibers 1, 2, 3).

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R. Bačovská et al. / Reactive and Functional Polymers 100 (2016) 53–63
Fig. 12. TGA curves of Ph-Me(t).
Higher contact angle values were obtained for nanolayers in the
Me(p) itself as a material for forming nanofibers. Ph-Me(p) dissolved
in THF can be electrospun into homogenic nanofibers which exhibit bet-
ter hydrophobic properties and higher thermal stability than the other
nanofibers described above.
It must also be mentioned that the synthesis of Ph-Me(p) is more
complicated than the synthesis of Ph-Me(t) and so it must be consid-
ered, whether to use the combination of organic polymers and the Ph-
Me(t) additive or whether using Ph-Me(p) itself for creating nanofibers
is more suitable for practical application.
presence of the Ph-Me(t) additive (in combination with all the afore-
mentioned commercial polymers =Fibers 2) than for nanolayers
made only from commercial polymers without the Ph-Me(t) additive
(Fibers 1). The mere fact that nanofibers can be created from commer-
cial polymers enriched with the Ph-Me(t) additive leads to the expan-
sion of their application possibilities.
Although the use of Ph-Me(t) in commercial polymers improves the
hydrophobic properties of nanofibers, it has been proposed to use Ph-
Fig. 13. TGA curves of Ph-Me(p).

R. Bačovská et al. / Reactive and Functional Polymers 100 (2016) 53–63
63
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Table 4
The comparison of minimum thermal decomposition temperatures from TGA for poly-
meric nanofibers with and without Ph-Me(t).
a
a
Fibers composition
Tad (°C)
Td polymer–Td
polymer+Ph-Me(t)
PA6
342
153
200
210
210
90
230
225
320
110
−189 °C
+10 °C
−120 °C
−5 °C
PA6 + Ph-Me(t)
PS
PS + Ph-Me(t)
ASA
ASA + Ph-Me(t)
SAN
SAN + Ph-Me(t)
PESU
−210 °C
PESU + Ph-Me(t)
Tad = Minimum thermal decomposition temperature from TGA.
−/+ = the value of decrease/increase of Tad.
Acknowledgments
FR-TI1/413, Ministry of Industry & Trade, and LO1411 (CEPLANT
plus), Ministry of Education, Youth and Sports of the CR/National Feasi-
bility Program I.
This SEM analysis has been supported by the project LO1411 (NPU
I) funded by Ministry of Education Youth and Sports of Czech Republic.
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