Electron-beam Initiated Polymerization of Elemental Phosphorus
TARASOVA N.P., ZANIN A.A., KRIVOBORODOV E.G.
UNESCO chair in Green Chemistry for Sustainable Development
Mendeleev University of Chemical Technology of Russia
125047, Moscow, Miusskaya Square, 9
RUSSIA
Abstract: - The article discusses the results of the synthesis of polymer phosphorus from the elemental phosphorus
in the aqueous medium under the electron-beam irradiation. The structure of the obtained high-molecular
phosphorus-containing compounds was analyzed and compared with samples of commercially available red
phosphorus by mass spectrometry with matrix-activated laser desorption/ionization.
Key-Words: - radiation chemistry, phosphorus, red phosphorus, radiation polymerization, phosphorus-containing
polymers, electron accelerator
Received: July 9, 2022. Revised: August 19, 2023. Accepted: September 25, 2023. Published: November 2, 2023.
1 Introduction
The modern state-of-art of chemistry of inorganic
polymers, polymeric forms of phosphorus among
them, is characterized by the development of
fundamental and applied research aimed at obtaining
target products with predictable properties. First of
all, it should include modification of the structure and
composition of inorganic polymers, variation of
reaction initiation methods (e.g., chemical, thermal or
high-energy initiation), as well as that of the reaction
medium thus contributing to the formation of the
desired structure of the final product. Recently, there
has been an increased interest in the modification of
red phosphorus, due to the significant expansion of
the fields of application of this inorganic polymer [1-
5].
2 Problem Formulation
Specific features of white phosphorus (high
reactivity, fire and explosion hazards, toxicity) [6]
make us look for milder conditions for obtaining red
phosphorus. The use of high-energy radiation is one
of the most interesting methods for initiating red
phosphorus synthesis reactions. Its advantages and
disadvantages can be identified in comparison with
traditional thermal methods, however, it is obvious
that only radiation initiation makes it possible to
polymerize white phosphorus in various
environments with the least fire risks.
Mendeleev University of Chemical Technologies of
Russia has been developing this scientific direction
for more than 40 years, the goal of which is to find
alternative conditions for the conversion of white
phosphorus into a polymer form, for example, under
the influence of high-energy radiation [7-11]. Based
on the obtained results and taking into account the
experience of using electron beam radiation in
polymer chemistry [12-17], it was decided to conduct
a study of the polymerization process of elemental
phosphorus under the influence of electron beam
radiation in an aqueous medium in the presence of
air.
3 Problem Solution
White phosphorus, purified with potassium
bichromate, was placed in quartz glass tubes half
filled with water, hermetically rolled up and
irradiated at the electron accelerator "Electronics"
UELV-10-10-S-70 (with magnetron MI-470). The
irradiation was carried out by a beam of accelerated
electrons with the energy of 7 MeV. Dosimetry was
performed using a standard sample of the absorbed
dose of proton and electron radiation SO PD(F)E-
5/50. To isolate the resulting product, multiple
purification in a Soxlet extractor was used, after
which the samples were analyzed by MALDI-ToF
technique using a mass-spectrometer Ultraflex II
(Bruker) in the reflective mode on positive ions
without the use of a matrix with an accelerating
voltage of 25 keV. Desorption was performed by an
Nd:YAG laser beam ( = 355 nm). Also, the structure
of the obtained phosphorus-containing polymers was
characterized by X-ray fluorescent analysis (Bruker
Kappa APEX DUO). The interpretation of the
obtained spectra and the identification of individual
peaks were carried out using the FlexAnalysis-3.3
program. The characteristics of the studied samples
are presented in Table 1.
International Journal of Chemical Engineering and Materials
DOI: 10.37394/232031.2023.2.11
Tarasova N. P., Zanin A. A., Krivoborodov E. G.
E-ISSN: 2945-0519
77
Volume 2, 2023
Table 1. Characteristics of the studied samples
№
Weight
before
irradiation,
g
Reaction
medium
Yield,
%
1
2,48
H2O/air
oxygen
3.9
2
2,50
H2O/air
oxygen
8.0
3
2,10
H2O/air
oxygen
11,5
4
2,55
H2O/air
oxygen
13,5
To identify the structure and composition of the
obtained samples, their MALDI-TOF spectra were
compared with the MALDI-TOF spectrum of
commercially available red phosphorus ("Reachim",
purity over 99%), Fig. 1.
Fig. 1. MALDI-TOF spectrum of commercially
available red phosphorus.
There is a series of intense signals in the spectrum
(Fig. 1) that differs by 61.94 Da, which corresponds
to two phosphorus atoms. The sample does not
contain impurities, since the values of the signals
correspond exactly to the masses of the fragments of
the polymer chain, for example, the most intense
signal with m/z = 774.368 corresponds to a fragment
of the P25 chain with a calculated mass of 774.344 Da.
The MALDI-TOF spectra of phosphorus-containing
polymers obtained at different irradiation doses after
irradiation at the electron accelerator are similar in
many ways. For this reason, the discussion of the
results will be conducted using Sample 4 as an
example (Table. 1), obtained at the highest absorbed
radiation dose of 600 kGy (Fig. 2).
Fig. 2. MALDI-TOF spectrum of phosphorus-
containing polymer obtained using an electron
accelerator. The absorbed dose equals 600 kGy.
In the spectrum of the obtained phosphorus-
containing polymers (sample No. 4), the difference in
intense signals is also 61.95 Da, however, this value
does not correspond to two masses of phosphorus
atoms, but is divided into 32 and 30 Da, which
indicates the presence of additional elements in the
sample.
It is also worth paying attention to the mass of the
most intense signal with m/z = 528.650. The polymer
phosphorus fragment of the P17 chain has a calculated
mass of 526.55 Da and is present in the red
phosphorus spectrum (Fig. 1, 526.593 m/z signal),
which differs by 2 Da from the fragment with a mass
of 528.650 Da. Based on the combination of these
two facts, it can be assumed that the signal with m/z
= 528.650 corresponds to a fragment of the circuit
with the formula P15O4, This fact is confirmed by the
calculated data for such a structure: M(P15O4) =
528.586 Da. The pattern of polymer fragmentation
can be clearly observed as the result of the detailed
examination of several intense spectrum signals (Fig.
3).
Fig. 3. MALDI-TOF spectrum (710 – 780 m/z).of
phosphorus-containing polymer obtained using the
electron accelerator. The absorbed dose equals 600
kGy.
The signal 712.565 m/z corresponds to a fragment P23
of the polymer chain, which differs by 61.95 Da from
the fragment P25. Signals 714.599 m/z and 716.602
m/z were registered from fragments P21O4 and P19O8,
respectively, signals 744.582 m/z, 746.599 m/z,
International Journal of Chemical Engineering and Materials
DOI: 10.37394/232031.2023.2.11
Tarasova N. P., Zanin A. A., Krivoborodov E. G.
E-ISSN: 2945-0519
78
Volume 2, 2023
748.593 m/z - P23O2, P21O6, P19O10, and signals
776.561 m/z and 778.598 m/z are present in the
spectrum as a result of fragmentation of the oxidized
polymer chain with the formation of structural
components P23O4 and P21O8. The values of the
signals differ by 2, which allows us to confidently
consider these individual signatures as a set of
sequences of fragments of various phosphorus-
containing polymer chains, rather than single
ensembles of signals with isotopic distribution,
which is typical for samples with a high content of
organic materials.
It is likely that the appearance of oxygen in the
polymer chain of the obtained samples is associated
with the air environment and oxygen dissolved in
water, in which the polymerization was carried out.
According to the results of X-ray fluorescence
analysis, the atomic fraction of oxygen in the
phosphorus-containing polymers equals about 20 %.
4 Conclusion
The polymerization of white phosphorus in an
aqueous medium under the influence of an
accelerated electron beam results in the formation of
the high-molecular phosphorus containing
compound. The results of the MALDI-TOF and X-
ray fluorescence analysis of the samples obtained at
different absorbed doses suggest the presence of long
polymer chains of phosphorus in them, as well as
fragments containing oxygen.
Acknowledgement:
This research is supported by the Russian Science
Foundation. Project number 23-23-00543.
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Contribution of Individual Authors to the
Creation of a Scientific Article (Ghostwriting
Policy)
Natalia Tarasova formulated the idea and edited the
manuscript
Alexey Zanin has organized and executed the
experiments of Section 3.
Efrem Krivoborodov analysed the experimental data
and wrote the text of the manuscript.
This research is supported by the Russian Science
Foundation. Project number 23-23-00543.
The authors have no conflicts of interest to declare
that are relevant to the content of this article.
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International Journal of Chemical Engineering and Materials
DOI: 10.37394/232031.2023.2.11
Tarasova N. P., Zanin A. A., Krivoborodov E. G.
E-ISSN: 2945-0519
80
Volume 2, 2023