S. Annam et al.
Reactive and Functional Polymers 131 (2018) 203–210
was packed with 6 g of CMPO functionalised crosslinked polymer resin
and preconditioned with 6 M nitric acid solution A synthetic mixture of
functionalised with CMPO derivatives. The resonance signals at
183 ppm and 175 ppm belongs to the amide and ester carbonyl groups
present in CMPO ligand and crosslinker respectively. Likewise, multiple
signals in the range of 40–70 ppm and 135 ppm correspond to the alkyl
groups and phenyl groups of CMPO. The existence of phosphoryl
(P=O) moiety in the polymer matrix was confirmed by P CP-MAS
NMR spectra (Fig. 1b). The resonance signals were observed at
28.1 ppm for P]O, along with sidebands at 114 and − 58 ppm, these
results clearly confirm the presence of CMPO derivatives covalently
bonded to the crosslinker.
−
1
−1
thorium (100 mg L ) and (200 mg L ) uranium solution was pre-
pared in 6 M nitric acid solution for the column studies and the loading
studies were carried out with a flow rate of ∼10 mL/h at room tem-
perature (30 °C). The concentration of metal ions in the effluent samples
during loading of U(VI) and Th(IV) was estimated by spectro-
photometry using thorin [43] and Br-PADAP [44] as chromogenic
agents at 545 ± 1 nm and 578 ± 1 nm for thorium and uranium re-
spectively. The purity of the eluted samples were analysed by HPLC
using 0.05 M 2-hydroxy isobutric acid as a mobile phase with pH -4.
3
1
FT-IR spectra of the polymers 5a-c (Fig. S34, ESI) shows the typical
−
1
−1
adsorption bands at 1114 cm
1
(P=O), 1438 cm
(CeN str.),
627 cm (C]O (amide)), 1722 cm (C]O (ester)). Fig. 2 shows the
thermal properties of crosslinked polymers 5a-c. From the TG curves
Fig. 2a), the degradation of polymers involves two main processes. The
−1
−1
3. Results and discussion
(
3
.1. Synthesis and characterization of CMPO functionalised crosslinked
first stage of decomposition at around 100 °C can be accounted for the
volatilization of physisorbed water. The second stage at around 300 °C,
corresponds to the decomposition of ligand moieties tethered to the
crosslinker. Fig. 2b shows the DSC profile of the three crosslinked
polymers
2-Chloro N,N-dialkyl acetamides 2a-c [45] were synthesized by
reacting secondary amines with chloroacetyl chloride at lower tem-
peratures, which further reacted with diphenyl phosphine oxide in the
presence of aliquat-336 to give corresponding diphenyl-N, N-dialkyl
carbamoylmethylphosphine oxide 3a-c. [46] As depicted in the Scheme
polymers 5a-c. No obvious T was detected for the polymers 5a-c, due
to the high degree of cross-linking (35%). From the DSC-TGA curves, it
is clearly evident that the CMPO-functionalised crosslinked polymers
showed good thermal stability.
g
1
a, treatment of CMPO 3a-c with 4-vinyl benzyl chloride under basic
conditions yields corresponding vinyl anchored CMPO monomers 4a-c
in good yields. [47] The compounds thus synthesized (2a-c, 3a-c and
3.2. Screening of porogen in polymer synthesis
4
a-c) were characterized by NMR and GC–MS (for spectral data see ESI,
Fig. S1- S33).
Unequivocal confirmation of the structure of 4c is provided by X-ray
In polymer synthesis, porous properties of polymers fairly depend
on the type and concentration of porogens. Owing to the importance of
porogens on pore volume and pore size of the polymers, different sol-
vents viz., chloroform, toluene, N, N-dimethyl formamide and 1,4-di-
oxane were employed. The resulted polymers were subjected to ni-
trogen gas adsorption-desorption studies and was found to be
mesoporous (2–50 nm), isotherms were shown Fig. 3 and the physical
properties are listed in Table S2 (ESI). Among the synthesized polymers
the usage of 1,4-dioxane resulted in large volume and ordered pore. The
surface morphology of the polymers prepared in different porogens was
evaluated by SEM analysis. As shown in (Fig. S35, ESI), a polymer
prepared in chloroform resulted as agglomerated spherical beads,
whereas the sheet-like morphology was observed in DMF, toluene and
1,4-dioxane.
analysis (CCDC no. 1499017, Scheme 1b). Complete crystal data and
structure refinement details for monomer 4c are given in the Table S1,
ESI. Furthermore, the synthesis of CMPO functionalized crosslinked
polymers 5a-c was achieved using precipitation polymerization tech-
nique [48]. For instance, the polymer 5a was prepared by reacting
CMPO monomer 4a (65 wt%) with crosslinker EGDMA (35 wt%) in the
presence of radical initiator AIBN (1 wt% to the monomer) (For detailed
experimental procedures see ESI).
The structural integrity, the presence of functional groups in the
polymer matrix and thermal stability of the polymers were confirmed
by the CP-MAS NMR, FT-IR and elemental analysis. Fig.1a shows the
1
3
C
CP-MAS NMR spectra of cross-linked polymer materials
Fig. 1. Overlay (a) 13C CP-MAS; (b) 31P CP-MAS NMR spectra of CMPO functionalised crosslinked polymers 5a-c.
205