Silicon-containing poly(esters) with halogenated bulky side groups. Synthesis, characterization and thermal studies

Article abstract of DOI:10.1039/c5ra06896g

Poly(esters) (PEs) derived from diacids containing bulky side groups, which have an halogenated (Cl, Br) imide ring, an aminoacidic residue (glycine, l-alanine, l-valine) and an amide group were obtained with a silicon-containing diphenol. Also PEs without the aminoacidic residue were obtained. PEs were characterized by IR and NMR spectroscopy, and the results were in agreement with the proposed structures. PEs were obtained with good yields and moderate or high η_inh values. PEs were soluble in aprotic polar solvents and were swollen in other solvents like m-cresol and THF. The T_g values were determined and it was possible to see a tendency in the sense that when the size of the atom (Cl, Br) bonded to the imidic ring is increased, the T_g values decreased, also for those PEs obtained without the aminoacidic residue. The thermal decomposition temperatures showed that only two PEs can be considered as thermostable, considering TDT values above 400°C at 10% of weight lost. The other PEs showed good thermal stability, showing in general a decrease of the TDT values when the volume of the side group, is increased. PEs showed UV-vis transparency at 400 nm lower than 20%, but between 500 and 600 nm, showed 80% transparency. PEs containing halogen atoms showed flame retardancy in a simple essay, with respect to PEs without halogen atoms in which the combustion was complete.

Full text of DOI:10.1039/c5ra06896g

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Silicon-containing poly(esters) with halogenated
bulky side groups. Synthesis, characterization and
thermal studies
Cite this: RSC Adv., 2015, 5, 49132
L. H. Tagle, C. A. Terraza, A. Tundidor-Camba and D. Coll
Poly(esters) (PEs) derived from diacids containing bulky side groups, which have an halogenated (Cl, Br)
imide ring, an aminoacidic residue (glycine, L-alanine, L-valine) and an amide group were obtained with
a silicon-containing diphenol. Also PEs without the aminoacidic residue were obtained. PEs were
characterized by IR and NMR spectroscopy, and the results were in agreement with the proposed
structures. PEs were obtained with good yields and moderate or high hinh values. PEs were soluble in
aprotic polar solvents and were swollen in other solvents like m-cresol and THF. The Tg values were
determined and it was possible to see a tendency in the sense that when the size of the atom (Cl, Br)
bonded to the imidic ring is increased, the Tg values decreased, also for those PEs obtained without
the aminoacidic residue. The thermal decomposition temperatures showed that only two PEs can be
considered as thermostable, considering TDT values above 400 ꢀC at 10% of weight lost. The other
PEs showed good thermal stability, showing in general a decrease of the TDT values when the volume
of the side group, is increased. PEs showed UV-vis transparency at 400 nm lower than 20%, but
between 500 and 600 nm, showed 80% transparency. PEs containing halogen atoms showed flame
retardancy in a simple essay, with respect to PEs without halogen atoms in which the combustion was
complete.
Received 16th April 2015
Accepted 21st May 2015
DOI: 10.1039/c5ra06896g
www.rsc.org/advances
structural modications, which include amino acids as exible
units with bulky groups and several functional groups,
increasing the exibility due to the central sp3 carbon of the
1. Introduction
Poly(esters) are condensation polymers which have been
considered of interest due to their excellent mechanical prop-
erties, chemical resistance and thermal stability.1–4 However,
when poly(esters) have high aromatic content, the processing is
difficult due to high Tg values and insolubility in common
organic solvents.5–9
There are several structural changes that are possible to
introduce into the monomers with the objective to improve the
polymeric properties. In this sense the introduction of exible
units in the main or side chain, or cardo groups, are solutions
proposed in order to increase the solubility and to decrease the
Tg values, but without affecting the thermal stability.10–13
Cardo or bulky side groups have the objective of to reduce
the intermolecular interactions between the polymeric chains
due to the higher free volume, and consequently it is possible to
improve the solubility and to decrease the Tg due to the higher
internal mobility of the polymeric chains. One of the groups
used with this objective is the imide one.2,5,14
amino acid moiety.15
Silicon-containing condensation polymers also have been
developed in order to introduce in the polymeric chain
heteroatoms which induce polarity in the main chain due to the
difference of electronegativity between Si and C, increasing the
solubility. These polymers have been studied for potential
applications due to that the Si atom permits a s–p conjugation
when it is between aromatic rings and consequently participate
in the electron transport in the polymeric chain.13,16,17 In this
sense, Thames16,18 and Bruma19,20 have described silicon-
containing polymers, with good solubility in common organic
solvents and low Tg values, but maintaining the thermal
stability.
The presence of halogen atoms in the polymeric chains
also has been studied. In general atoms like Cl or Br can to act
as ame retardant because they can remove free radicals,
which diminish the burning process.21 Mallakpour has
described polymers with this property, including bulky
groups and halogen atoms, which led to ame-retardant
materials, with good solubility, without affect the thermal
properties.22
On the other hand, the introduction of exible groups in the
repeating unit also has been used in order to improve the
processability. Mallakpour has described poly(esters) with
Continuing our works about the synthesis and character-
ization of silicon-containing condensation polymers,23–27 in this
´
Ponticia Universidad Catolica de Chile, Faculty of Chemistry, Organic Chemistry
Department, P.O. Box, 306, Santiago, Chile. E-mail: ltagle@uc.cl
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ꢁ1
ꢀ
ꢀ
ꢀ
work we describe the synthesis of poly(esters) (PEs) derived 30 C and 800 C with a heating rate of 20 C min under N2
from diacids containing a bulky side group, which have an ow. Specic rotations were measured in an Optical Activity
imidic ring substituted with halogen atoms (Cl or Br), an ami- Automatic polarimeter, Model AA-5 at 17 ꢀC. The UV-visible
noacidic residue (glycine, L-alanine or L-valine) and an amide optical transmission spectra were obtained in NMP solutions
group.
(c ¼ 5.0 g Lꢁ1) at room temperature on a UV-3101PC UV-Vis-NIR
These carboxylic imide-acids were polymerized with bis(4- scanning spectrophotometer (Shimadzu, Japan). Elemental
hydroxyphenyl)dimethylsilane and the poly(esters) were char- analyses were made on a Fisons EA 1108-CHNS-O equipment.
acterized by elemental analysis, IR and NMR spectroscopy. The
thermal properties, Tg and TDT, were determined and the
results were related with the proposed structures. Also UV-vis
transparency and ame resistance were determined.
2.3. Monomer synthesis
The carboxylic imide-acids: phthalimidyl-acetic acid (H-I-a),28
tetrachlorophthalimidyl-acetic acid (Cl-I-a),29 tertrabromophtha-
limidyl-acetic acid (Br-I-a),30 2-phthalimidyl-propanonic acid (H-
2. Experimental
2.1. Materials
I-b),31 2-tetrachlorophthalimidyl-propanoic acid (Cl-I-b),29,32 2-
tetrabromophthalimidyl-propanoic acid (Br-I-b),30,32 2-phtha-
limidyl-3-methyl-pentanoic
phthalimidyl-3-methyl-pentanoic acid (Cl-I-c),29,32 and 2-
tetrabromophthalimidyl-3-methyl-pentanoic acid (Br-I-c),30,32
acid
(H-I-c),33
2-tetrachloro-
Glycine, L-alanine, L-leucine and p-amino-benzoic acid, 5-
amino-isophthalic acid and the anhydrides phthalic, tetra-
chlorophthalic and tetrabromophthalic, were obtained from
Aldrich Chemical (Milwaukee, WI) and used without further
purication. All other reagents and solvents were purchased
commercially as analytical-grade and used without further
purication.
were
obtained
from
the
respective
phthalic-
or
tetrahalophthalic-anhydrides and the corresponding amino
acid, according to a general procedure, in which the phthalic- or
tetrahalophthalic-anhydride (0.05 mol) (phthalic anhydride
7.4 g, tetrachlorophthalic anhydride 14.3 g or tetrabromoph-
thalic anhydride 23.2 g) was mixed with the amino acid
(0.05 mol) (glycine 3.8 g, L-alanine 4.5 g, or L-leucine 6.5 g) in
50 mL of acetic acid and stirred during four hours. Then the
mixture was reuxed by four hours and the acetic acid removed
under vacuum. The residue was poured in 50 mL of a 10% HCl
solution and the solid ltered, washed several times with water,
dried under vacuum until constant weight (Scheme 1). The
2.2. Instrumentation
The IR spectra (KBr pellets) were recorded on a Perkin-Elmer
(Fremont CA) 1310 spectrophotometer over the range of
450–4000 cmꢁ1. 1H, 13C and 29Si NMR spectra were carried out
on a 400 MHz instrument (Bruker AC-200) using DMSO-d6,
CDCl3 or acetone-d6 as solvents and TMS as the internal stan-
dard. Viscosimetric measurements were made in a Desreux–
Bischof type dilution viscosimeter at 25 C (c ¼ 0.5 g dLꢁ1). Tg
ꢀ
values were obtained with a Mettler-Toledo (Greifensee, Swit-
zerland) DSC 821 calorimetric system (20 ꢀC minꢁ1 under N2
ow) aer the second heating run. Thermogravimetric analyses
were carried out in a Mettler (Switzerland) TA-3000 calorimetric
system equipped with a TC-10A processor, and a TG-50 ther-
mobalance with a Mettler MT5 microbalance. Samples of
6–10 mg were placed in a platinum sample holder and the
thermogravimetric measurements were carried out between
Scheme 2 Synthesis of the dicarboxylic imide-acids X-III.
Scheme 1 Synthesis of the dicarboxylic imide-amide-acids X-II-(a-c).
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Scheme 3 Synthesis of poly(esters) X-PE-(a-c) and poly(esters) X-PE.
nature of all compounds was veried by IR and 1H and 13C NMR are stirred by 30 minutes. Aer this time, a mixture of 4.1 mmol
spectroscopy. of 4-toluenesulfonyl chloride (Tos-Cl), 0.97 mL of pyridine and
The dicarboxylic imide-amide-acids: 5-(phthalimidyl- 0.39 mL of DMF, with a standby of 30 minutes, is added at room
acetylamino)-isophthalic acid (H-II-a),28 5-(tetrachloroph- temperature and the reaction mixture is stirred for 30 minutes.
thalimidyl-acetylamino)-isophthalic acid (Cl-II-a),34 5-(tetra Then, the mixture is heated at 90 ꢀC for 10 minutes and a
bromophthalimidyl-acetylamino)-isophthalic acid (Br-II-a),34 5- solution of 0.82 mmol of the silylated diphenol in 0.97 mL of
(2-phthalimidyl-propionylamino)-isophthalic acid (H-II-b),31 5- pyridine is added. Now, the mixture is stirred for 3 hours at
(2-tetrachlorophthalimidyl-propionylamino)-isophthalic acid 90 ꢀC. Then the mixture is poured into water and the solid
(Cl-II-b),34 5-(2-tetrabromophthalimidyl-propionylamino)-iso- ltered, washed, and dried under vacuum until constant weight
phthalic acid (Br-II-b),34 5-(2-phthalimidyl-4-methyl-pentanoyl- and characterized (Scheme 3).
amino)-isophthalic acid (H-II-c),33 5-(2-tetrachlorophthalimidyl-
4-methyl-pentanoylamino)-isophthalic acid (Cl-II-c),34 and 5-
(2-tetrabromophthalimidyl-4-methyl-pentanoylamino)-isophthalic
acid (Br-II-c),34,35 were obtained from the respective carboxylic
phthalimidyl- or tetrahalophthalimidyl-acids according to a
general procedure, in which the carboxylic imide acid was
mixed with thionyl chloride in order to obtain the acid chloride,
which reacted with 5-amino-isophthalic acid. The mixture was
poured in 10% HCl solution, and the solid ltered, washed with
water and dried until constant weight (Scheme 1). The nature of
all compounds was veried by IR and 1H and 13C NMR
spectroscopy.
PEs derived from phthalic anhydride
H-PE-a.
The dicarboxylic imide-acids: 5-phthalimidyl-isophthalic
diacid (H-III),28 5-tetrachlorophthalimidyl-isophthalic diacid
(Cl-III),38,39 and 5-tetrabromophthalimidyl-isophthalic diacid
(Br-III),34 were obtained by reaction of the respective phthalic- or
tetrahalophthalic-anhydrides and 5-amino-isophthalic acid
(Scheme 2) according to the same former procedure already
described. The nature of all compounds was veried by IR and
1H and 13C NMR spectroscopy.
IR (KBr) (cmꢁ1): 3429 (NH), 3070 (CH arom.), 2947 (CH3), 1772,
(C]O imide), 1735 (C]O ester), 1699 (C]O amide), 1596, 1577
(C]C arom.), 1454 (CH3), 1425 (Si–C arom.), 1371 (Si–C aliph.),
1102 (O–C arom.), 839 (arom. 1,3,5-subst.), 820 (arom. p-subst.).
1H NMR (DMSO-d6) (d) (ppm): 0.59 (s, 6H, CH3) (21), 4.54 (s, 2H,
CH2) (5), 7.34 (s, 4H, arom.) (18), 7.64 (s, 4H, arom.) (19), 7.87–
7.91 (m, 4H, arom.) (3, 4), 8.46 (s, 1H, arom.) (15), 8.56–8.60 (s,
2H, arom.) (13), 11.10 (s, 1H, NH) (11). 13C NMR (DMSO-d6) (d)
(ppm): ꢁ3.4 (21), 38.7 (5), 120.6 (18), 122.6 (3), 124.7 (15), 129.5
The diphenol bis(4-hydroxyphenyl)dimethylsilane was
synthesized from 4-bromophenol and dimethyldichlorosilane,
according to a describe procedure.36
2.4. Polymer synthesis and characterization
PEs were synthesized according to the following general
procedure. In a typical polymerization process, 0.82 mmol of
the monomeric diacid are dissolved in 1.92 mL of pyridine and
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(13), 130.3 (2), 130.8 (4), 134.0 (14), 134.6 (20), 135.0 (12), 144.6
(19), 150.7 (17), 162.4 (16), 165.1 (10), 166.7 (1). 29Si NMR
(DMSO-d6) (d) (ppm): ꢁ7.84 (22). Elemental analysis. Calcu-
lated: (C32H24N2O7Si) (576.64 g molꢁ1): C: 66.65%, H: 4.20%, N:
4.86%. Found: C: 66.46%, H: 4.28%, N: 4.61%.
H-PE-b.
H-PE. X ¼ H
IR (KBr) (cmꢁ1): 3467 (NH), 3089 (CH arom.), 2952 (CH3),
1778, (C]O imide), 1727 (C]O ester), 1588 (C]C arom.), 1453
(Si–C arom.), 1372 (Si–C aliph.), 1110 (O–C arom.), 877 (arom.
1,3,5-subst.), 834 (arom. p-subst.). 1H NMR (DMSO-d6) (d)
(ppm): 0.6 (s, 6H, CH3) (21), 7.36 (s, 4H, arom.) (18), 7.64 (s, 4H,
arom.) (19), 7.95 (m, J ¼ 25.5, 4H, arom.) (3, 4), 8.6 (s, 2H, arom.)
(13), 8.78 (s, 1H arom.) (15). 13C NMR (DMSO-d6) (d) (ppm): ꢁ2.3
(21), 121.4 (18), 123.5 (3), 125.5 (15), 128.1 (13), 130.5 (2), 131.5
(4), 134.3 (14), 134.8 (20), 135.3 (12), 135.7 (19), 151.4 (17), 163.0
(16), 166.6 (1). 29Si NMR (DMSO-d6) (d) (ppm): ꢁ7.79 (22).
Elemental analysis. Calculated: (C30H21NO6Si) (591.58 g molꢁ1):
C: 69.35%, H: 4.07%, N: 2.70%. Found: C: 69.30%, H: 4.11%, N:
2.28%.
IR (KBr) (cmꢁ1): 3448 (NH), 3095 (CH arom.), 2954 (CH3), 1775,
(C]O imide), 1735 (C]O ester), 1637 (C]O amide), 1588, 1559
(C]C arom.), 1450 (CH3), 1425 (Si–C arom.), 1370 (Si–C aliph.),
1109 (O–C arom.), 916 (arom. 1,3,5-subst.), 824 (arom. p-subst.).
1H NMR (DMSO-d6) (d) (ppm): 0.58 (s, 6H, CH3) (21), 1.57 (s, 3H,
CH3) (6), 4.99 (m, 1H, CH) (5), 7.32 (s, 4H, arom.) (18), 7.62 (s,
4H, arom.) (19), 7.84 (m, 4H, arom.) (3, 4), 8.44 (s, 1H, arom.)
(15), 8.70 (s, 2H, arom.) (13), 10.41 (s, 1H, NH) (11). 13C NMR
(DMSO-d6) (d) (ppm): ꢁ2.6 (21), 14.9 (6), 48.9 (5), 121.3 (18),
123.1 (3), 125.5 (15), 129.3 (13), 130.3 (2) 131.8 (4), 134.4 (14),
135.3 (20), 135.6 (12), 140.0 (19), 151.6 (17), 163.5 (16), 167.2
(10), 168.4 (1). 29Si NMR (DMSO-d6) (d) (ppm): ꢁ7.85 (22).
PEs derived from tetrachlorophthalic anhydride
Cl-PE-a.
IR (KBr) (cmꢁ1): 3433 (NH), 3072 (CH arom.), 2954, 1450 (CH3),
1784, (C]O imide), 1727 (C]O ester), 1628 (C]O amide), 1598
(C]C arom.), 1450 (CH3), 1416 (Si–C arom.), 1371 (Si–C aliph.),
1110 (O–C arom.), 914 (arom. 1,3,5-subst.), 833 (arom. p-subst.),
680 (C–Cl). 1H NMR (DMSO-d6) (d) (ppm): 0.41 (s, 6H, CH3) (21),
4.12 (m, 1H, CH2) (5), 6.32 (s, 4H arom.) (18), 6.85 (s, 4H, arom.)
(19), 8.04 (s, 1H, arom.) (15), 8.91 (s, 2H, arom.) (13), 10.39 (s,
1H, NH) (11). 13C NMR (DMSO-d6) (d) (ppm): ꢁ2.0 (21), 42.9 (5),
123.3 (18), 123.4 (15), 127.4 (13), 128.9 (2), 129.9 (3), 137.2 (14),
137.3 (4), 139.6 (20), 140.7 (12), 147.5 (19), 153.4 (17), 160.3 (1),
160.5 (16), 164.8 (10). 29Si NMR (DMSO-d6) (d) (ppm): ꢁ7.80 (22).
Elemental analysis. Calculated: (C32H20Cl4N2O7Si) (714.40 g
molꢁ1): C: 53.80%, H: 2.82%, N: 3.92%. Found: C: 53.84%, H:
2.78%, N: 3.89%.
Elemental analysis. Calculated: (C33H26N2O7Si) (590.66
g
molꢁ1): C: 67.10%, H: 4.44%, N: 4.74%. Found: C: 67.15%, H:
4.39%, N: 4.64%.
H-PE-c.
Cl-PE-b.
IR (KBr) (cmꢁ1): 3432 (NH), 3088 (CH arom.), 2952, 2871, 1496
(CH3, CH2), 1775 (C]O imide), 1742 (C]O ester), 1606 (C]O
amide), 1589, 1545 (C]C arom.), 1496 (CH3), 1467 (Si–C
arom.), 1368 (Si–C aliph.), 1111 (O–C arom.), 915 (arom. 1,3,5-
subst.), 834 (arom. p-sust.). 1H NMR (DMSO-d6) (d) (ppm):
0.23 (s, 3H, CH3) (21), 0.53 (s, 3H, CH3) (210), 0.83–0.88 (d, J ¼
17.7 MHz, 6H, CH3) (9), 1.40 (m, 1H, CH) (8), 2.00 (m, 1H, CH2)
(7), 2.13 (m, 1H, CH) (70), 4.94 (m, 1H, CH) (5), 7.27 (s, 4H,
arom.) (18), 7.58 (s, 4H, arom.) (19), 7.82–7.87 (m, 4H, arom.)
(3, 4), 8.42 (s, 1H, arom.) (15), 8.67 (s, 2H, arom.) (13), 10.41 (s,
1H, NH) (11). 13C NMR (DMSO-d6) (d) (ppm): ꢁ3.4 (21), 20.2 (9),
22.38 (90), 23.9, (8), 36.2 (7), 51.07 (5), 120.7 (18), 122.6 (3),
124.7 (15), 127.3 (13), 129.3 (2), 133.5 (4), 133.9 (14), 134.5 (20),
134.8 (12), 139.2 (19), 150.8 (17), 162.7 (16), 166.9 (10), 167.5
(1). 29Si NMR (DMSO-d6) (d) (ppm): ꢁ8.01 (22). Elemental
analysis. Calculated: (C36H32N2O7Si) (632.74 g molꢁ1): C:
68.34%, H: 5.10%, N: 4.43%. Found: C: 68.25%, H: 5.07%, N:
4.39%.
IR (KBr) (cmꢁ1): 3432 (NH), 3071 (CH arom.), 2953, 1391 (CH3),
1782, (C]O imide), 1727 (C]O ester), 1627 (C]O amide),
1588, 1513 (C]C arom.), 1451 (Si–C arom.), 1368 (Si–C aliph.),
1391 (CH3), 1110 (O–C arom.), 914 (arom. 1,3,5-subst.), 825
(arom. p-subst.), 680 (C–Cl). 1H NMR (DMSO-d6) (d) (ppm): 0.58
(s, 6H, CH3) (21), 1.59 (d, 3H, CH3) (6), 5.04 (m, 1H, CH) (5), 7.32
(s, 4H, arom.) (18), 7.62 (s, 4H, arom.) (19), 8.45 (s, 1H, arom.)
(15), 8.69 (s, 2H, arom.) (13), 10.42 (s, 1H, NH) (11). 13C NMR
(DMSO-d6) (d) (ppm): ꢁ2.7 (21), 14.4 (6), 49.1 (5), 121.3 (18),
125.4 (15), 128.0 (13), 128.1 (2), 130.1 (3), 135.2 (14), 137.6 (4),
138.4 (20), 139.8 (12), 145.3 (19), 151.4 (17), 162.6 (1), 163.4 (16),
167.6 (10). 29Si NMR (DMSO-d6) (d) (ppm): ꢁ7.82 (22). Elemental
analysis. Calculated: (C33H22Cl4N2O7Si) (728.43 g molꢁ1): C:
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54.41%, H: 3.04%, N: 3.85%. Found: C: 54.39%, H: 3.17%, N:
Br-PE-b.
3.79.
Cl-PE-c.
IR (KBr) (cmꢁ1): 3432 (NH), 3072 (CH arom.), 2951 (CH3), 1777,
(C]O imide), 1724 (C]O ester), 1627 (C]O amide), 1587, 1560
(C]C arom.), 1451 (CH3), 1408 (Si–C arom.), 1370 (Si–C aliph.),
1108 (O–C arom.), 822 (arom. p-sust.), 918 (arom. 1,3,5-sust.),
669 (C–Br). 1H NMR (DMSO-d6) (d) (ppm): 0.58 (s, 6H, CH3) (21),
1.55 (d, 3H, CH3) (6), 5.04 (m, 1H, arom.) (5), 7.32 (s, 4H, arom.)
(18), 7.62 (s, 4H, arom.) (19), 8.45 (s, 1H, arom.) (15), 8.68 (s, 2H,
arom.) (13), 10.36 (s, 1H, NH) (11). 13C NMR (DMSO-d6) (d)
(ppm): ꢁ2.11 (21), 14.95 (6), 49.71 (5), 121.1 (18), 122.0 (3), 126.0
(15), 128.5 (13), 130.6 (14), 131.5 (4), 135.8 (20), 136.1 (12), 137.1
(19), 140.4 (2), 151.9 (17), 163.5 (1), 163.9 (16), 168.3 (10). 29Si
NMR (DMSO-d6) (d) (ppm): ꢁ7.80 (22). Elemental analysis.
Calculated: (C33H22Br4N2O7Si) (906.25 g molꢁ1): C: 43.74%, H:
2.45%, N: 3.09%. Found: C: 43.78%, H: 2.39%, N: 3.10%.
Br-PE-c.
IR (KBr) (cmꢁ1): 3432 (NH), 3071 (CH arom.), 2954, 2852, 1452
(CH3, CH2), 1777 (C]O amide) 1725 (C]O ester), 1626 (C]O
amide), 1587, 1570 (C]C arom.), 1452 (CH3), 1419 (Si–C arom.),
1371 (Si–C aliph.), 1111 (O–C arom.), 910 (arom. 1,3,5-subst.),
834 (arom.-p-subst.), 680 (C–Cl). 1H NMR (DMSO-d6) (d) (ppm):
0.60 (s, 6H, CH3) (21), 0.92 (d, 6H, CH3) (9), 1.57 (m, 1H, CH) (8),
2.28 (m, 2H, CH2) (7), 5.00 (m, 1H, CH) (5), 7.33 (s, 4H, arom.)
(18), 7.64 (d, 4H, arom.) (19), 8.46 (s, 1H, arom.) (15), 8.70 (s, 2H,
arom.) (13), 10.52 (s, 1H, NH) (11). 13C NMR (DMSO-d6) (d)
(ppm): ꢁ2.7 (21), 20.7 (9), 20.9 (90), 23.1, (8), 36.73 (7), 52.4 (5),
121.4 (18), 123.8 (15), 125.4 (13), 128.0 (2), 128.3 (3), 135.3 (14),
137.5 (4), 138.5 (20), 145.5 (12), 149.5 (19), 151.4 (17), 163.0 (1),
163.4 (16), 167.5 (10). 29Si NMR (DMSO-d6) (d) (ppm): ꢁ7.80 (22).
Elemental analysis. Calculated: (C36H28Cl4N2O7Si) (770.51 g
molꢁ1): C: 56.12%, H: 3.66%, N: 3.64%. Found: C: 56.23%, H:
3.54%, N: 3.71%.
Cl-PE. X ¼ Cl
IR (KBr) (cmꢁ1): 3434 (NH), 3071 (CH arom.), 1786, (C]O
imide), 1735 (C]O ester), 1588, 1587 (C]C arom.), 1451 (Si–
C arom.), 1369 (Si–C aliph.), 1108 (O–C arom.), 918 (arom.
1,3,5-subst.), 824 (arom. p-sust.). 1H NMR (DMSO-d6) (d)
(ppm): 0.60 (s, 3H, CH3) (21), 7.35 (s, 4H, arom.) (18), 7.64 (s,
4H arom.) (19), 8.55 (s, 1H, arom.) (15), 8.83 (s, 2H, arom.)
(13), 13C NMR (DMSO-d6) (d) (ppm): ꢁ2.7 (21), 121.3 (18),
125.4 (15), 128.0 (13), 128.2 (2), 128.4 (3), 130.7 (14), 132.5 (4),
135.3 (20), 135.7 (12), 138.6 (19), 151.3 (17), 162.2 (1), 162.8
(16). 29Si NMR (DMSO-d6) (d) (ppm): ꢁ7.8 (22). Elemental
analysis. Calculated: (C30H17Cl4NO6Si) (657.35 g molꢁ1): C:
54.82%, H: 2.61%, N: 2.13%. Found: C: 54.79%, H: 2.57%, N:
2.22%.
IR (KBr) (cmꢁ1): 3433 (NH), 3066 (CH arom.), 2956, 2870, 1450
(CH3, CH2), 1778 (C]O, imide), 1723 (O–C arom.), 1627 (C]O
amide), 1587, 1544 (C]C arom.), 1450 (CH3), 1424 (Si–C arom.),
1368 (Si–C aliph.), 1109 (C–O ester), 916 (arom. 1,3,5-subst.),
1
823 (arom. p-sust.), 681 (C–Br). H NMR (DMSO-d6) (d) (ppm):
0.59 (s, 6H, CH3) (21), 0.90–0.91 (m, 6H, CH3) (9, 90), 1.56 (m, 1H,
CH) (8), 2.06 (m, 1H, CH2) (7), 2.28 (m, 1H, CH2) (70), 4.99 (m,
1H, CH) (5), 7.33 (s, 4H, arom.) (18), 7.63 (d, 4H, arom.) (19),
8.46 (s, 1H, arom.) (15), 8.69 (s, 2H, arom.) (13), 10.42 (s, 1H,
NH) (11). 13C NMR (DMSO-d6) (d) (ppm): ꢁ2.8 (21), 23.2 (9), 25.0
(90), 26.5, (8), 39.0 (7), 54.8 (5), 122.8 (18), 123.4 (3), 127.5 (15),
128.4 (13), 129.9 (14), 132.3 (4), 132.9 (20), 137.3 (12), 137.6 (19),
138.8 (2), 153.6 (17) (C arom.), 165.3 (1), 165.5 (16), 169.6 (10).
29Si NMR (DMSO-d6) (d) (ppm): ꢁ7.10 (22). Elemental analysis.
Calculated: (C36H28Br4N2O7Si) (948.33 g molꢁ1): C: 45.60%, H:
2.98%, N: 2.95%. Found: C: 45.63%, H: 2.92%, N: 2.89%.
Br-PE. R: 67%. IR (KBr) (cmꢁ1): 3433 (NH), 3084 (H arom.),
2952, 1495 (CH3), 1770, (C]O imide), 1730 (C]O ester), 1587
(C]C arom.), 1495 (CH3), 1452 (Si–C arom.), 1370 (Si–C aliph.),
1107 (O–C arom.), 917 (arom. 1,3,5-subst.), 821 (arom. p-sust.),
673 (C–Br). 1H NMR (DMSO-d6) (d) (ppm): 0.60 (s, 6H, CH3) (21),
7.36 (s, 4H, arom.) (18), 7.65 (s, 4H, arom.) (19), 8.56 (s, 2H,
arom.) (13), 8, 82 (s, 1H, arom.) (15), 13C NMR (DMSO-d6) (d)
(ppm): ꢁ2.8 (CH3) (21), 122.9 (18), 123.3 (3), 130.0 (15), 132.4
PEs derived from tetrabromophthalic anhydride
Br-PE-a.
IR (KBr) (cmꢁ1): 3435 (NH), 3070 (CH arom.), 2951, 1450 (CH3),
1776, (C]O imide), 1728 (C]O ester), 1626 (C]O amide), 1597
(C]C arom.), 1450 (CH3), 1414 (Si–C arom.), 1371 (Si–C aliph.),
1108 (O–C arom.), 914 (arom. 1,3,5-subst.), 832 (arom. p-sust.),
669 (C–Br). Elemental analysis. Calculated: (C32H20Br4N2O7Si)
(892.22 g molꢁ1): C: 43.08%, H: 2.26%, N: 3.14%. Found: C:
43.19%, H: 2.21%, N: 3.03%.
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(13), 132.9 (14), 133.1 (4), 135.4 (20), 137.4 (12), 137.8 (19), 138.8
The IR spectra showed the disappearance of the O–H
(2), 153.5 (17), 162.3, 162.7 (C]O). 29Si NMR (d) (ppm) (DMSO- stretching band associated to a carboxylic acid group and the
d6): ꢁ7.83. Elemental analysis. Calculated: (C30H17Br4NO6Si) appearance of a new band between 1740–1724 cmꢁ1 corre-
(835.17 g molꢁ1): C: 43.14%, H: 2.05%, N: 1.68%. Found: C: sponding to the C]O stretching of the ester group. Other
43.16%, H: 2.00%, N: 1.53%.
specic absorption bands for the polymers are listed in the
Experimental Part.
When it corresponds, the 1H NMR spectra showed the
aliphatic signals of the aminoacidic residue with the expected
and integration values. All PEs showed a singlet at about
0.5 ppm provided by the two CH3 groups magnetically equiva-
lent bonded to the Si atom of the diphenol moiety. The silicon
atom shis the signal at high eld due to its lower electroneg-
ativity in relation to the carbon atom. For the same polymers,
the aromatic zone was very complex due to the overlapping of
signals. Thus, the AB systems proposed for H18 and H19 appear
like a broad singlet, however, the integration values were in
agreement with the hydrogen number atoms.
3. Results and discussion
3.1. Monomer synthesis and characterization
The monoacids X-I-(a-c) were obtained from the respective
phthalic anhydrides and the amino acids glycine, L-alanine and
L-valine according to described procedures.28–32 (Scheme 1) The
diacids X-II-(a-c) were synthesized by the reaction of acid chlo-
rides of these monoacids with 5-amino-isophthalic acid
according to previous works.28,31,33–35 (Scheme 2) The
dicarboxylic imide-acids X-III were prepared by reaction of the
respective phthalic anhydrides and 5-amino-isophthalic acid.
All of the monomeric diacids were characterized and the results
were in agreement with the proposed structures.
The signals in 13C NMR spectra of polymers were assigned
based on the spectra of monomers. The aromatic region pres-
ents a great number of C aromatic and the CH3 groups bonded
to the Si atom appear between ꢁ2.1 and ꢁ3.4 ppm due to the
electronic effect of the heteroatom above discussed. The spectra
clearly show at low magnetic eld the carbonyl groups provided
by the amide, imide and ester functions that ratied the
structure of the polymeric samples.
3.2. Polymer synthesis and characterization
PEs were obtained according to the procedure described by
Higashi37 showed in the Scheme 3 in which a Tos-Cl and
DMF-pyridine mixture was used as polymerizing system. This
method of direct polycondensation consists in the reaction of
the diacid with a Vilsmeier adduct, which is prepared with Tos-
Cl, pyridine in DMF. This adduct was aged previous to its use
acting as activator agent of the diacids groups of the monomer
and allowing this way the reaction with the silylated diphenol.
PEs were obtained with almost quantitative yields (94–98%)
and the particular values for each run are summarized in Table
1. Apparently, the presence of the halogen atoms in the phthalic
ring moiety does not affect the nal reactivity of the dicarboxylic
aids.
For all PEs the 29Si spectra were obtained, which showed only
one signal at about ꢁ7 and ꢁ8 ppm approximately. This shi
has been described in compounds in which the silicon atom is
part of a –Ph–Si(CH3)2–Ph-unit.38 Fig. 1 shows as an example the
1H, 13C and 29Si NMR spectra of PE-Cl-b.
When the formation of lms was attempted, the products
were brittle materials and inadequate for mechanical tests.
All the PEs including L-alanine and L-valine showed optical
rotation (levorotatory) and the results are summarized in Table 1.
3.3. Inherent viscosity and solubility
The structure of the repetitive unit of the polymers was
characterized by means of elemental analysis and spectroscopic Table 2 shows the results of the solubility tests for the PEs.
techniques. Thus, the C, N and H percentage contents in all Almost all the PEs were soluble in aprotic polar organic solvents
samples are in agreement with the expected values.
at room temperature, such as DMAc, DMF, DMSO and NMP,
Table 1 I. Yields, [a]D, hinh, Tg and TDT of the poly(esters)e
hinh (dL gꢁ1
)
Tg (ꢀC)
TDT (ꢀC)
Rc (%)
LOId
a
b
c
Yield (%)
[a]D (ꢀ)
H-PE-a
H-PE-b
H-PE-c
Cl-PE-a
Cl-PE-b
Cl-PE-c
Br-PE-a
Br-PE-b
Br-PE-c
H-PE
94
95
96
98
98
95
97
98
97
94
97
95
—
0.27
1.03
0.23
0.48
0.76
0.35
0.75
0.39
0.45
0.35
0.27
0.45
219
160
70
154
96
146
114
96
402
375
380
338
353
288
234
329
341
403
372
367
44
33
27
40
30
32
28
27
22
24
39
32
35.1
30.7
28.3
33.5
29.5
30.3
28.7
28.3
26.3
27.1
33.1
30.3
ꢁ43
ꢁ31
—
ꢁ51
ꢁ28
—
ꢁ39
ꢁ25
—
nd
110
nd
Cl-PE
Br-PE
—
—
105
a
In N,N-dimethylformamide at 25 ꢀC. b Inherent viscosity, in NMP at 25 ꢀC (c ¼ 0.5 g dLꢁ1). c Residue at 800 ꢀC. d Limiting oxygen index. e nd: not
determined.
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Fig. 1 1H, 13C and 29Si NMR spectra (400 MHz, DMSO-d6) of poly(ester) Cl-PE-b.
and the rest were partially soluble at 40 ꢀC and/or showed
3.4. Thermal properties
swollen. In other solvents as m-cresol or THF, only PEs without
an aminoacidic residue was soluble at 40 ꢀC, and the others only
showed swollen. Apparently, the aminoacidic moiety dimin-
ishes the polarity of the chain increasing its solubility. All PEs
were insoluble in other solvents as CHCl3 or alcohols.
Table 1 also shows the Tg values obtained for the PEs. If the
inuence of the atoms bonded to the imide ring (H, Cl, Br) is
analyzed, it is possible to see that when the size of this atom is
increased, the Tg values decrease, due probably to higher
separation between the polymeric chains which confers them
more mobility. The exception to this rule was the PEs series with
L-valine as aminoacidic residue, which showed a high value for
Cl-PE-c and a low value for H-PE-c. For the series without ami-
noacidic residue, also it was possible to see a slight decrease of
the Tg when the atom of the imidic ring increased in size, with
the exception of Cl-PE whose Tg was not detected. Fig. 2 shows
the Tg values of PEs which include glycine in the structure.
On the other hand, if the nature of the amino acid is
considered, also it is possible to see a tendency. When the
volume of the side group is increased, the Tg values decreases,
due probably to a less symmetry and higher chain exibility.
This fact would imply less packing forces inter-chains which
permit the segmental motions and consequently lower Tg
values. The exception was Cl-PE-c, including L-valine as ami-
noacidic residue.
Table 1 also shows the inherent viscosity values (hinh),
obtained in NMP at 25 ꢀC and 0.5 g dLꢁ1 as concentration. The
registered values were moderate to high, obtaining the highest
value for H-PE-b of 1.03 dL gꢁ1. In general, the highest hinh
values were obtained for PEs for which the monomeric diacids
were soluble in pyridine at room temperature. The higher
solubility would be transferred to the polymer in the reaction
media, which permits the growing of the chains. The monomer
solubility can be conditioned to the volume of the halogen
atoms, in the sense that when it volumes increased, the
carboxylic diacids have higher separation which would permit
good solvation. This effect can be observed for PEs including
glycine (a) or L-valine (c), but not for those with L-alanine (b) in
which the hinh values decreases when the size of the halogen
increases. In this aspect, the effect of the amino acid was not
clear.
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Table 2 Solubility of the poly(esters) PEsa
Polymer
DMSO
NMP
DMF
DMAc
m-Cresol
THF
H-PE-a
Cl-PE-a
Br-PE-a
H-PE-b
Cl-PE-b
Br-PE-b
H-PE-c
Cl-PE-c
Br-PE-c
H-PE
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
H
ꢂH
ꢂH
+
+
+
+
+
+
H
H
H
H
H
H
H
H
H
+
H
H
H
H
H
H
H
H
H
+
ꢂH
H
ꢂH
ꢂH
ꢂ
+
+
+
+
+
+
ꢂ
ꢂH
+
+
+
+
+
+
+
Cl-PE
Br-PE
+
+
ꢂ
ꢂ
+
ꢁ
+
a
+: soluble at room temperature. ꢂ: soluble at 40 ꢀC. H: swollen. ꢂH:
only a part of the sample was soluble at 40 ꢀC, the rest was swollen.
ꢁ: insoluble.
Fig. 2 Tg of poly(esters) H-PE-a, Cl-PE-a and Br-PE-a (second scan,
20 ꢀC minꢁ1 under N2 flow).
In general the same behavior was observed for poly(amides)
derived from the same dicarboxylic acid with an aromatic
diamine containing Si as central atom.28,34
The thermal degradation temperatures (TDT) of the PEs were
determined, for which was considered the temperature at which
the polymer lost 10% of weight. In general, a polymer is
considered as thermostable when the weight loss is less than
10% at 400 ꢀC.
3.5. Optical properties
The optical transparency of the PEs was determined from the
transmittance, which depends on the wavelength of the inci-
dent light. A sample is considered as transparent when the
transmittance at 400 nm is higher than 80%. In the case of
organic polymers with a high aromatic content like these PEs,
there are interactions between the p electrons of the aromatic
rings which absorb energy in the UV-vis region, and as a
consequence the materials can be colorless with lower trans-
parency. In this work the transparence was measured in solu-
According to the above denition, only two PEs can be
considered as thermostable, H-PE-a and H-PE. The other PEs
showed lower values, but can be considered with good thermal
stability, due principally to the great aromatic content of the
repeating unit and the micropolarity contributed by the Si–C
bond. If the inuence of the amino acid is considered, there is
not a clear tendency of the TDT values. However, when the
inuence of atoms bonded to the imidic ring is analyzed, it is
possible to see that when the size of these atoms is increased (H,
Cl, Br), the TDT values decreased. Thus, the polymeric series
with Br shows the lowest TDT values with Cl-PE-c as the only
exception to this rule which showed a very low TDT value.
It is possible that when the size of the halogen atom is
increased from H to Br, the distance between the polymeric
chains also increased due to the higher volume of the imidic
side group. According to this, the interactions between the
chains are lower and the degradation process occurs at lower
temperatures. The same situation was possible to see in the PEs
without the aminoacidic moiety. In general, the exception was
the same to that observed for the Tg values. Fig. 3 shows the
results obtained for the degradation process for PEs which
include L-alanine in the structure. Also there are included the
respective derivative curves where is possible to evidence the
main degradation process of the chains at lower temperature
for the halogenated samples PE-H-b.
ꢁ1
ꢀ
tion of NMP at 15 C with a concentration of 0.5 g dL
.
For these PEs, the transparence at 400 nm was lower than
20%, but between 510 and 640 nm all polymers showed 80% of
transmittance. On the other hand, the cut-off wavelength of the
Table 1 also shows the residue (%) of the thermogravimetric
analysis at 800 ꢀC, which probably corresponds principally to
silicon oxide, but without to discard other inorganic
compounds due to the analysis was in N2 atmosphere.
Fig. 3 Thermal degradatꢁio1 n process for poly(esters) PE-H-b, PE-Cl-b
and Br-PE-b (20 ꢀC min under N2 flow).
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Table 3 Optical properties of the poly(esters) PEs
was stopped immediately. For those PEs without halogen atoms
in the repeating unit, the combustion continued until the
complete disappearance of the material.
PEs
T400 (%)
lT ¼ 80% (nm)
lcutoff (nm)
H-PE-a
H-PE-b
H-PE-c
H-PE
Cl-PE-a
Cl-PE-b
Cl-PE-c
Cl-PE
Br-PE-a
Br-PE-b
Br-PE-c
Br-PE
15.7
20.8
3.7
2.7
3.7
1.9
0.2
0.6
0.6
16.8
1.7
8.2
574
564
555
561
556
561
634
577
577
517
580
506
336
325
359
362
330
331
388
335
342
285
338
335
4. Conclusions
New poly(esters) containing an amide and/or imide group in the
side chain and halogen atoms (Cl or Br) bonded to the imide
ring, were synthesized from the respective dicarboxylic acids
and bis(4-hydroxyphenyl)dimethylsilane. Polymers were char-
acterized by elemental analysis, IR and H, 13C and 29Si NMR
1
spectroscopy and the results were in agreement with the
proposed structures.
PEs were obtained with good results yields and moderated
hinh values. The solubility was good in polar aprotic solvents
and some of them in THF. Almost of them showed swollen in
THF and m-cresol. These results were analyzed respect to the
presence of the halogen atom and when it corresponded, to the
nature of the aminoacidic moiety. In all cases, the different
interactions between the chains and therefore their solubility,
was related to the size of the halogen atom and side group of the
aminoacidic moiety.
The Tg and TDT values showed a tendency in the sense that
when the size of the halogen atom is increased, the values
decrease, due to the higher distance between the polymeric
chains, which increases their exibility and diminishes the
interactions between them.
samples is very similar and the obtained values are between 325
and 388 nm with the exception of Br-PE-b which presented a
lower value. These results are summarized in Table 3, and the
transparence curves are shown in the Fig. 4.
3.6. Flame retardancy
Halogen-containing materials are known as ame retardance,
due to that the free radicals responsible of the ame propaga-
tion are inhibited by the halogen atoms, which act in the
following order: I > Br > Cl > F.39 In Table 1 it is possible to see
the limiting oxygen index (LOI) calculated according to the Van
Krevelen and Hoyzer equation, in which R is the residue chart
PEs showed UV-vis transparence between 500 and 600 nm
approximately and those containing halogen atoms autoex-
tinction when were put at the ame.
at 800 C.40
ꢀ
LOI ¼ 17.5 + 0.4R
Acknowledgements
´
Authors acknowledge “Fondo Nacional de Investigacion
Also in this work a very simple essay was made, consisting in
to put the PE for 10 seconds in the ame. For all the PEs con-
taining Cl or Br when the ame was eliminated, the combustion
´
´
Cientıca y Tecnologica”, FONDECYT, through Project 1100015.
D.C. acknowledges CONICYT for a Ph.D, fellowship.
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