CO2_2016 - page 16

14
Chimica Oggi - Chemistry Today
- vol. 34(2) March/April 2016
requires case specific characterization and optimization
of the material properties, its preparation, processing and
recycling. Pulling these different elements together under
the common thread of FEAPM provides a central driving
force for the otherwise disconnected works and constitutes
the novelty of this research. Such an approach helps to
design novel biodegradable polymeric materials and to
avoid failures of the commercial products manufactured
from them. It also opens up wide opportunities for mass
spectrometry in FEAPM.
The use of environmentally friendly polymers as packaging
materials for long shelf-life applications such as cosmetic
packages is the new trend for production. However, ESI-MS
n
revealed that PLA degradation occurred not only in the
presence of polar organic solvents (ethyl alcohol, glycerine,
propylene glycol) but also in the presence of paraffin
because of the residual moisture content. Furthermore, the
degree of erosion of PLA-based rigid films was observed
to be strongly dependent on their blend composition
with synthetic (R,S)-PHB and the miscibility of these two
components (14).
ESI-MS
n
was successfully applied in the prediction study
dedicated to evaluation of the effect of the solvent-free
non-woven fabrics formation method on the release rate of
lactic and glycolic acids from the tin-free poly(lactide-co-
glycolide), PLGA, nonwovens (15). The results of the ESI-MS
n
sequencing of the PLGA samples remaining after hydrolytic
degradation indicated that the hydrolysis of ester bonds
reduces the degree of ordering of the macromolecules of
the PLGA copolymer (16).
FUTURE TRENDS - ESI-MS
n
FOR DECODING OF BIODEGRADABLE
POLYMERIC MATERIALS MOLECULAR LABELING
In general, the design of synthetic macromolecules
containing information can bs inspired by the biological
codes. In such an approach the monomers could be used
as coding units to implement information
in the polymer (17). This concept is very
difficult to be achieved in the case of high
molecular weight copolymers. Nevertheless,
it seems to be real at the level of synthetic
oligomers as it was demonstrated recently
for monodisperse sequence-encoded
poly(alkoxyamine amide) oligomers by Roy
et al (18).
The complete decoding of a sequence-
defined macromolecule may be achieved
by MS/MS sequencing. However, the MS/
MS dissociation patterns strongly depend
on the chemistry of the polymer backbone
(19-20). As mentioned above, the ESI-MS
n
technique was successfully applied for
sequencing of some PHA oligomers and thus
it provides information about the structure of
respective PHA copolymers at the molecular
level. Therefore, with the understanding of
the respective fragmentation patterns, the
basis for decoding of labeled biodegradable
polymer materials will have been created.
Currently in our laboratories the libraries of
monodisperse sequence-encoded PHA
oligomers are under development. The
molecular characterization of the low molecular weight
copolyesters by ESI MS
n
is particularly suitable when NMR,
the conventional technique for copolymer sequence
determination, requires spectral assignments for the reliable
interpretation.
The anionic ROP of
β
-substituted
β
-lactones seems to be
a perfect tool for the preparation of PHA analogues with
the desired molecular structure, and the co-monomeric
β
-lactones may be obtained by carbonylation of the
respective epoxides under CO at ambient pressure (9-11).
In systematic studies on the molecular level structures of
synthetic analogues of PHA, the ESI-MS
n
fragmentation
technique has been preferentially used because under such
experiments each co-monomer shows distinct fragmentation
pathways along the chain. It was originally reported that
diblock copolyesters may be differentiated from random ones
by the fragmentation patterns (12). As an example, the ESI-
MS
2
spectrum of the sodiated precursor ion m/z 1033 selected
from the simple ESI mass spectrum of diblock copolyester is
presented on Figure 2.
Further studies in this area are oriented on the bio-
functional PHA analogues containin bioactive compounds
incorporated into the polyester backbone. In this research,
the ESI-MS
n
sequencing revealed that fragmentation
of selected ions of potentially bioactive (co)oligoesters
proceeded by random breakage of ester bonds along the
oligomer chain as well as of the ester bonds of the bioactive
pendant groups (13).
ESI-MS
n
FOR FORENSIC ENGINEERING OF ADVANCED
BIODEGRADABLE POLYMERIC MATERIALS
Forensic engineering of advanced biodegradable
polymeric materials (FEAPM) deals with the evaluation of
the relationships between their structure, properties and
behaviour before, during and after practical applications
(14, 15). The diverse applications of biodegradable polymers
Figure 2.
ESI-MS
2
spectrum of the sodiated precursor ion [HB
5
/EMPL
4
+ Na]
+
, m/z
1033, selected from the simple ESI mass spectrum of diblock copolyester.
1...,6,7,8,9,10,11,12,13,14,15 17,18,19,20,21,22,23,24,25,26,...68
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