Article Cite This: Macromolecules XXXX, XXX, XXX−XXX
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Synthesis and Aggregation Behavior of Poly(arylene alkenylene)s and Poly(arylene alkylene)s Having Dialkoxyphenylene and Aromatic Diimide Groups Li Yi Tan,† Yoshitaka Tsuchido,† Kohtaro Osakada,† Zhengguo Cai,‡ Yoshiaki Takahashi,§ and Daisuke Takeuchi*,†,∥ †
Laboratory for Chemistry and Life Science, Tokyo Institute of Technology, R1-03, 4259 Nagatsuta, Yokohama 226-8503, Japan State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai 201620, P. R. China § Institute for Materials Chemistry and Engineering and Department of Molecular and Materials Sciences, Kyushu University, 6-1 Kasuga-koen, Kasuga, Fukuoka 816-8580, Japan ∥ Department of Frontier Materials Chemistry, Graduate School of Science and Technology, Hirosaki University, 3 Bunkyo-cho, Hirosaki, Aomori 036-8561, Japan
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‡
S Supporting Information *
ABSTRACT: Polycondensation reactions of 2,5-dialkoxy-1,4diiodobenzene with N,N′-ω-dialkenylpyromellitic diimide and N,N′-ω-dialkenyl naphthalenetetracarboxylic diimide in the presence of a Pd(OAc)2−NaOAc catalyst produce six polymers containing the two aromatic groups connected alternatingly by alkenylene spacers. 1H NMR spectrum of a polymer prepared from 2,5-bis(dodecyloxy)-1,4-diiodobenzene and N,N′-(10undecenyl)pyromellitic diimide (poly(1a-IA)) indicates that the polymerization involves 2,1- and 1,2-insertion of a vinyl group into the Pd−Ar bond in 70:30 selectivity. Matrix-assisted laser deportion/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) spectra of poly(1a-IA) and a polymer from 2,5bis(dodecyloxy)-1,4-diiodobenzene with N,N′-dialkenyl naphthalenetetracarboxylic diimide (poly(1a-IIA)) contained a series of polymer fragments with Mn up to 4500. Measurement of electrospray ionization MS (ESI-MS) of the polymers revealed formation of cyclic molecules for 1:1 and 2:2 oligomers. Hydrogenations of poly(1a-IA) by using [Ir(cod)(py)(PCy3)]+PF6− (cod = 1,5-cycloctadiene; PCy3 = tricyclohexylphosphine) catalyst and of poly(1a-IIA) by a mixture of p-toluenesulfonyl hydrazide (TSH) and tripropylamine (TPA) produce the poly(arylene alkylene)s with saturated spacers in 93% degree of hydrogenation. The absorption spectrum of poly(1a-IA) in CHCl3 shows an absorption edge at 410 nm, which is at a longer wavelength than that of a mixture of the monomers (370 nm). Light-scattering measurement of the solution (1.00 mmol L−1) indicates the presence of aggregates with a hydrodynamic radius of 48 nm. The polymers exhibit weak elasticity at room temperature, as determined by dynamic viscoelasticity analysis (DMA), and it becomes negligible on heating to 75−80 °C (polymer with pyromellitic diimide groups) and 110−122 °C (polymer with naphthalenetetracarboxylic diimide groups). The above properties of the polymers are attributed to attractive interaction between the electron-rich alkoxyphenylene and the electron-deficient aromatic diimide groups both in solution and in the solid state.
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INTRODUCTION
synthesis of the polymers composed of two different aromatic groups bonded with aliphatic spacers. Polymerization using an equimolar mixture of aromatic dihalides and aromatic compounds having two ω-alkenyl substituents affords poly(arylene alkenylene)s having the two aromatic groups separated by an alkenylene spacer. The reaction involves repetitive Mizoroki−Heck condensation, which includes β-hydride elimination of the alkyl-Pd species. Hydro-
Poly(arylene vinylene)s are π-conjugated polymers that exhibit light-emitting or nonlinear optical properties and have been studied as materials for optical devices.1 Among possible synthetic methods for poly(arylene vinylene)s, Mizoroki− Heck coupling polymerization provides a direct synthetic route from aromatic dihalides and divinyl arylenes or analogous π-conjugated diolefins.2−9 The use of aliphatic terminal diolefins instead of divinylbenzene derivatives would form poly(arylene alkenylene)s that contain alternating rigid aromatic groups and flexible aliphatic segments.10−13 Scheme 1 shows the strategy for © XXXX American Chemical Society
Received: November 18, 2018 Revised: January 19, 2019
A
DOI: 10.1021/acs.macromol.8b02468 Macromolecules XXXX, XXX, XXX−XXX
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Macromolecules Scheme 1. Synthesis of Poly(arylene alkenylene)s and Poly(arylene alkylene)s
Table 1. Results of Mizoroki−Heck Polycondensation monomers and polymerizationa
product
entry
I−Ar−I
diimide
solvent
1 2 3 4 5c 6 7 8d 9e 10f
1a(I)2 1a(I)2 1a(I)2 1a(I)2 1b(I)2 1c(I)2 1c(I)2 1c(I)2 1c(I)2 1c(I)2
IA(H)2 IB(H)2 IC(H)2 IIA(H)2 IA(H)2 IA(H)2 IA(H)2 IA(H)2 IA(H)2 IA(H)2
DMAc DMAc DMAc DMAc DMAc DMF DMSO DMAc DMAc DMAc
poly(1a-IA) poly(1a-IB) poly(1a-IC) poly(1a-IIA) poly(1b-IA) poly(1c-IA) oligo(1c-IA) poly(1c-IA) poly(1c-IA) oligo(1c-IA)
yield (%)
Mn (PDI)b
89 >99 96 94 89 89 68 91 trace 45
7600 (4.6)[7600 (4.3)] g g
3800 (1.7)[3800 (1.7)] 5100 (2.5)[5200 (2.5)] 5700 (2.0)[5700 (2.0)] 2200 (1.2)[2200 (1.2)] 5400 (2.1)[5500 (2.2)] 2000 (1.2)[2000 (1.2)]
Pd(OAc)2 = 0.025 mmol, I−Ar−I = 0.50 mmol, diimide = 0.50 mmol, NaOAc = 2.50 mmol, n-Bu4NBr = 1.1 mmol, solvent = 2 mL, 100 °C, 16 h. DMAc = dimethylacetamide. bMolecular weight by GPC (THF eluting, polystyrene standard, refractive index (RI) detector). Results by UV−vis detector are in brackets. cReaction at 80 °C for 22 h. dBase: i-Pr2EtN. eBase: Cs2CO3. fIn the absence of n-Bu4NBr. gNot measured owing to low solubility of the polymer. a
polycondensation exhibited optical and thermal properties caused by the intermolecular aggregation of the molecules, as presented in this Article.
genation of the CC double bond converts the polymers into poly(arylene alkylene)s having polymethylene spacers. The above procedure would afford the polymers containing two different aromatic cores bonded by flexible spacers. Aromatic diimide groups, such as pyromellitic diimide, were considered the core of rigid functional polymers with high thermal stability.14,15 The polymers composed of aromatic diimide groups and aliphatic spacers were prepared by solidstate thermal polycondensation of the salts of monomers.16 Their glass transition temperatures (Tg = 70−145 °C) were much lower than the common polyimides with aromatic spacers between the imide groups and varied depending on the diimide group and the length of the spacer. Recently, a few research groups reported the polymers having aromatic diimide core bonded with aliphatic spacers and their intra- and intermolecular π−π stacking interaction with the other aromatic groups. Lokey Iverson designed a polymer composed of dialkoxyarylene and aromatic diimide groups connected with hydrophilic spacers and observed intramolecular stacking of the electron-rich and -deficient aromatic groups and the consequent preference for a folded conformer.17 Regulation of conformation by interactions has also been reported for ionenes.18 Rowan and co-workers combined a polymer having aromatic diimide groups and one having perylene terminals and designed healable materials on the basis of intermolecular donor−acceptor interaction.19,20 Similar interactions of the electron-rich and -deficient aromatic groups were observed in the molecules containing aromatic diimide groups and spacers.21,22 A new polymer with both electron-rich and -deficient aromatic groups bonded with polymethylene spacers is expected to be aggregated in solution because of the intermolecular π−π stacking between the two different aromatic rings. We chose the dialkoxyarylene and aromatic diimide groups as the two aromatic groups, Ar1 and Ar2, in Scheme 1. The polymers synthesized by Mizoroki−Heck
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RESULTS AND DISCUSSION
Polymerization and Hydrogenation. The monomers were synthesized in accordance with the previously reported method.23−27 Diiodoarenes with two alkoxy substituents reacted with N,N′-dialkenylarylene diimide in the presence of a catalytic amount of Pd(OAc)2−NaOAc, as shown in eq 1.
B
DOI: 10.1021/acs.macromol.8b02468 Macromolecules XXXX, XXX, XXX−XXX
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Macromolecules Scheme 2. Possible Partial Structures (i−v) and Model Compounds for the NMR Assignment (vi−viii)
Table 1 shows the monomers used and the results of polymerization.28,29 Polycondensation of 2,5-bis(dodecyloxy)1,4-diiodobenzene (1a(I) 2 ) with N,N′-(10-undecenyl)pyromellitic diimide (IA(H)2) for 16 h at 100 °C formed poly(1a-IA) in 89% yield (Mn = 7600, PDI = 4.6, entry 1). A reaction for 20 h at 100 °C yielded the polymer sparingly soluble in CHCl3 and tetrahydrofuran (THF) at room temperature. Soxhlet extraction separated it into warm THF-soluble and -insoluble fractions in 78:22 ratio, and the former one is with a smaller molecular weight (Mn = 5100, PDI = 2.7) than the polymer before the extraction. Polycondensation reactions of 1a(I)2 with IB(H)2 and IC(H)2 resulted in the formation of the corresponding polymers, and the products with C8 and C4 carbon spacers are insoluble in organic solvents (entries 2 and 3). The polymer of 1a(I)2 and N,N′-(10-undecenyl)-1,4,5,8naphthalenetetracarboxylic diimide (IIA(H)2) was soluble in THF, and GPC measurement in the solvent showed Mn = 3800 (entry 4). Polymers containing pyromellitic diimide (poly(1a-IA), poly(1a-IB), and poly(1a-IC)) appeared red in the solid state, while the polymer containing the naphthalenetetracarboxylic diimide group (poly(1a-IIA)) appeared deep purple. DMAc was a suitable solvent for most of the polymerization reactions examined. NaOAc worked as a better base to trap evolved HI than i-Pr2EtN (entry 8). Use of Cs2CO3 as a base did not form polymer products (entry 9). The reaction without addition of nBu4NBr resulted in a low polymer yield (entry 10). Scheme 2(i−v) shows possible partial structures of the polymers. The Mizoroki−Heck reaction via 2,1-insertion of the vinyl group into a Pd−Ar bond, followed by β-hydride elimination, forms an arenylidene group (i), whereas the C−C bond formation followed by chain-walking of the polymer−Pd bond prior to β-hydride elimination yields both Ar−CH2−CH2 group and vinylene (CC) group in the spacer (ii and iii). 1,2-Insertion of the vinyl group of the monomer and β-hydride elimination lead to a vinylidene group attached to the aromatic group, shown in (iv). 1,2-Insertion accompanied by chainwalking yields structures (iii) and (v). Figure 1 shows the 1H NMR spectrum of poly(1a-IA) (entry 1, Table 1). Signals were assigned by comparing the peak
Figure 1. 1H NMR of poly(1a-IA) (500 MHz, CDCl3, rt). Hf and Hg can be reversed.
position with those of the model compounds, namely, (E)-3(2,5-dimethoxy-4-methylphenyl)propenol (Scheme 2 vi),30 2(2,5-dimethoxy-4-methylphenyl)propene (vii),31 and 4-octene (viii).32 Signals of OCH2 and NCH2 hydrogens were observed at 3.72 and 3.87 ppm, respectively. A minor signal at 7.10 ppm was assigned to an iodophenyl group at the end group of the polymer molecule. The arenylidene group (Scheme 2(i)) gave rise to signals of vinylene hydrogens (Ha and Hb) at 6.85 and 6.16 ppm. The benzyl hydrogens of structure (ii) give rise to the signal at 2.52 ppm (Hc). A larger signal at 5.3−5.5 ppm was assigned to the vinylene hydrogens in the polymethylene spacer ((iii) Hd and He). This internal olefin group was formed via 1,2- and 2,1-insertion of a vinyl group of the monomer or oligomer into the Pd−Ar bond followed by chain walking. The resulting −(CH2)2−CHPd− (CH2)2− group underwent β-hydride elimination to form the vinylene group. Initial 1,2-insertion of a vinyl group into a Pd− Ar bond and direct β-hydride elimination yielded a vinylidene group (iv), which corresponded to the signals at 5.04 and 4.98 ppm (Hf and Hg). A sequence involving 1,2-insertion, chainwalking, and β-hydride elimination formed the 1-arylethyl group (v), and a signal of the arenylidene hydrogen Hh was observed at 3.25 ppm. The ratio of the intensities of the signals from the partial structures attached to the aromatic ring (i, ii, iv, and v) was estimated to be 35:35:9:21. A model reaction for the C−C bond-forming reactions was examined by using 2-bromophenylhexyl ether and N-(6-heptenyl)phthalimide as the substrates C
DOI: 10.1021/acs.macromol.8b02468 Macromolecules XXXX, XXX, XXX−XXX
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Macromolecules Scheme 3. 1:1 and 2:2 Oligomers from 1a(I)2 and IIA(H)2
and Pd(OAc)2−NaOAc as the catalyst. The product contained the structures corresponding to (i, ii, iv, and v) at a ratio of 32:26:8:34 as determined on the basis of NMR signals corresponding to Ha−Hc and Hf−Hh of the polymer (positions of the peaks related to the structures: 6.67, 6.21, 5.30−5.45, 5.07, 4.97, 3.15, and 2.58 ppm). Thus, 2,1- and 1,2-insertion of the vinyl group into the Pd−Ar bond occurs in 70:30 ratio in the polymerization and in 58:42 ratio in the model reaction. The ratios are much lower than the reported Mizoroki−Heck reactions of aryl halides with vinyl arenes. MALDI-TOF-MS spectra of poly(1a-IA) and poly(1a-IIA) contain peaks of serieses of the molecules with Mn up to 4500 (Figures S12 and S13). Poly(1a-IA) is composed of the molecules with two vinylic terminal groups and the molecules with the terminal group without an iodine substituent. The spectrum of poly(1a-IIA) shows peaks corresponding to the two
above series of molecules and a series of peaks due to equimolar oligomers having an iodoarene terminal group. Measurement of the ESI-MS spectroscopy of poly(1a-IA) and poly(1a-IIA) (Figures S14 and 15) provided detailed information on the structure of the equimolar oligomers without iodo substituent. The 1:1 oligomers show the highest peaks ([M + Na]+) at 985.6987 (poly(1a-IA)) and 1035.7161 (poly(1a-IIA)). The isotope pattern for 1:1 oligomer suggests formation of the cyclic oligomer (Scheme 3(i)) as a major component and the linear oligomers with hydrogenated aromatic terminal (Scheme 3(ii)) in a much smaller amount. The 2:2 oligomers are composed of those with a cyclic structure (Scheme 3(iii)) or a catenane structure formed by two interlocked 1:1 cyclic oligomers (Scheme 3(iv)) in a much higher amount than the linear molecule (Scheme 3(v)). D
DOI: 10.1021/acs.macromol.8b02468 Macromolecules XXXX, XXX, XXX−XXX
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Macromolecules Scheme 4. Possible Intermediates for Cyclic Oligomers
Formation of the 1:1 cyclic oligomer is facilitated by attractive interaction of the electron-rich bis(alkoxy)phenylene group and electron-deficient aromatic diimide group, as schematically shown in Scheme 4(i). Parts ii and iii of Scheme 4 show possible intermediates to form the 2:2 cyclic oligomer and catenane oligomer, respectively. Minor linear oligomers with deiodinated aromatic terminal group are formed via an aryl-palladium intermediate that does not react further with a vinyl group and abstracts a hydrogen from solvent or substrate molecules. The oligomers with cyclic structures and with a deiodinated aryl terminal render the averaged molecular weight of the reaction product lower than expected from the polycondensation reactions of equimolar bifunctional monomers. Hydrogenation of the poly(arylene alkenylene) containing pyromellitic diimide groups using a transition metal complex catalyst produced the poly(arylene alkylene) having polymethylene spacers, as shown in eq 2. Polymers obtained by ring-opening metathesis polymerization of cyclic olefins and by metathesis polymerization of terminal dienes were hydrogenated to produce the polymers with saturated alkylene groups. The reactions were carried out by using transition metal catalysts or by using organic reducing agents such as toluenesulfonyl hydrazide (TSH) in the presence of tripropylamine (TPA).13,33,34 Table 2 summarizes the results of the reaction. Hydrogenation of poly(1a-IA) catalyzed by [Ir(cod)(py)(PCy3)]+PF6− formed the polymer with saturated spacers, poly(1a-IA-H) (93% hydrogenated) (entry 1).
Hydrogenation of the polymer using TSH/TPA gave uncharacterized polymers probably owing to the undesired side reactions of the pyromellitic diimide groups. The polymer containing naphthalenetetracarboxylic diimide groups, poly(1aIIA), underwent efficient hydrogenation by TSH in the presence of TPA to yield poly(1a-IIA-H) (entry 2). Poly(aryl alkenylene)s with shorter substituents on the phenylene groups, poly(1b-IA) and poly(1c-IA), were also hydrogenated by using [Ir(cod)(py)(PCy3)]+PF6− as the catalysts, and RhCl(PPh3)3 does not catalyze the hydrogenation of the former polymer E
DOI: 10.1021/acs.macromol.8b02468 Macromolecules XXXX, XXX, XXX−XXX
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Macromolecules Table 2. Hydrogenation of Polymers before hydrogenation entry
polymer
d
poly(1a-IA)
2e
poly(1aIIA) poly(1bIA) poly(1bIA) poly(1c-IA)
1
3f 4g 5h
Mn (PDI)a 5600 (4.1) [5700 (4.3)] 3800 (1.7) [3800 (1.7)] 5100 (2.5) [5200 (2.5)] 5100 (2.5) [5200 (2.5)] 4100 (2.0) [4100 (2.1)]
after hydrogenation
catalyst
conditions
yield (%)
degree of hydrogenationb (%)
[Ir(cod)(py) (PCy3)]+PF6− TSH/TPA
60 °C, 72 h
98
93
64/36
130 °C, 24 h 50 °C, 24 h
90
93
70/30
90
78
64/36
80 °C, 72 h
90
440 nm) and the peak position of the polymer with naphthalene imide groups is at a much longer-wavelength position than that with pyromellitic diimide groups. The absorption peak of poly(1a-IIA-H) is at a longer-wavenumber position than that of poly(1a-IIA) before hydrogenation, while polymer poly(1a-IA) shows the absorption peak at a similar position to that of the hydrogenated polymer poly(1a-IA-H). The results of measurement of the absorption spectra indicate that the dialkoxyphenylene and aromatic diimide groups have donor−acceptor interaction both in solution and in the solid state. The solution at 1.00 mmol L−1 contains colloidal particles formed via aggregation of the polymer molecules. The absorption spectra of the polymers in the solid state contain clear peaks at the visible region, while the spectra in solution show a significant shift of the absorbance edge to a longerwavelength region in solution. Figure 5 shows the wide-angle X-ray diffraction diagrams of a series of polymers before and after hydrogenation. Diffraction at 2θ = 20° corresponds to the layer spacing between aromatic groups in all the polymers.16 The estimated distance between
(entries 3−5). The polymers after hydrogenation have similar molecular weights to the polymers before the hydrogenation. NMR spectra of the hydrogenated polymers clarified structures between the spacer and the aryl group. Two possible structures, the Ar−CH2−CH2− and Ar−CH(CH3)− groups, were formed from 2,1- and 1,2-insertion reactions, respectively, in the polymerization. The 13C{1H} NMR spectrum of poly(1aIA-H) (Figure 2a) contains signals from −CH− and −CH3 carbons of the latter branched structure at 37.64 and 21.03 ppm, respectively. The 1H NMR spectrum shows the corresponding signals at 3.10 and 1.16 ppm (Figure 2b). Although the latter signal markedly overlapped with a large signal of CH2 hydrogen, 1 H−1H correlation spectroscopy (COSY) confirmed the signal assignment. The ratio of Ar−CH2−CH2− to Ar−CH(CH3)− was determined to be 64:36 on the basis of the 1H NMR peak area ratio between the signals from CH hydrogen (3.10 ppm) and to those from CH2−Ar hydrogens of the repeating unit (2.53 ppm). Polymer Properties. Figure 3 shows absorption spectrum of poly(1a-IA) in CHCl3 solution (1.00 mmol L−1) as well as the spectra of the monomers and their equimolar mixture at similar concentrations. 1,4-Bis(dodecyloxy)benzene, 1a(H)2, and pyromellitic diimide with ω-alkenyl groups at the nitrogen atoms, (IA)H2, show absorption maxima assigned to π−π* transition at 290 and 305 nm, respectively. The spectrum of the polymer includes peaks of the two absorptions, and the absorption edge (410 nm) is at a longer wavelength than that of an equimolar mixture of the two aromatic compounds (370 nm). Light-scattering measurement of a solution of poly(1a-IA) (CHCl3, 1.00 mmol L−1) revealed the presence of colloidal particles with an averaged hydrodynamic radius of 48 nm (Figure S16). These results suggest that intermolecular interaction between the two aromatic groups in the polymer chain causes entanglement of the molecules and formation of the aggregates supported by stacking of aromatic rings.35 De and Ramakrishnan reported an ionic polymer containing 1,5alkoxynaphthylene groups and pyromellitic diimide groups connected by alkylene spacers equipped with a quaternary ammonium group.18 The molecule adopts a zigzag conformation stabilized by intramolecular interaction between the electron-rich dialkoxynaphthylene group and the electronF
DOI: 10.1021/acs.macromol.8b02468 Macromolecules XXXX, XXX, XXX−XXX
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Macromolecules
Figure 2. (a) 13C{1H} NMR spectrum of poly(1a-IA-H) (125 MHz, CDCl3, rt) and (b) 1H NMR and 1H−1H COSY spectra of poly(1a-IA-H) (500 MHz, CDCl3, rt).
Glass transition temperatures are influenced more significantly by the alkoxy substituents on the phenylene group than by the presence (or absence) of CC double bonds in the spacers. DSC of the poly(arylene alkenylene)s showed only glass transition. In contrast, a melting point was observed for the poly(arylene alkylene)s. Hydrogenation of the CC bond of the spacer increases the crystallinity of the polymer. The crystallinity was also affected by alkoxy groups; an exothermic peak appeared for poly(1a-IA-H), which has longer alkoxy substituents than poly(1a-IB-H). The speed of formation of crystals is slower in such a case. Polyimides with soft spacers
the aromatic groups (ca. 4.3 Å) is consistent with that between the two aromatic groups with π−π stacking.36,37 Poly(1a-IC) with a much shorter spacer also showed diffraction at 2θ = 20°, although the diffraction is much weaker. DSC analyses were applied for the poly(arylene alkenylene)s and poly(arylene alkylene)s obtained in this study (Figure 6). Poly(1a-IA) and poly(1a-IA-H) with bis(dodecyloxy)phenylene and pyromellitic diimide groups underwent glass transitions at −28 and −27 °C, respectively. Poly(1b-IA) and poly(1b-IA-H) with bis(hexyloxy)phenylene and pyromellitic diimide groups showed Tg values at 0 and −6 °C, respectively. G
DOI: 10.1021/acs.macromol.8b02468 Macromolecules XXXX, XXX, XXX−XXX
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Macromolecules
Figure 6. Results of differential scanning calorimetry (DSC) measurement (2nd, 10 °C/min heating). Dotted line shows glass transition temperatures; poly(1a-IA) Tg = −28 °C, poly(1a-IA-H) Tg = −27 °C, poly(1b-IA) Tg = 0 °C, poly(1b-IA-H) Tg = −6 °C.
Figure 3. Absorption spectra of 1a(H)2, IA(H)2, an equimolar mixture of 1a(H)2 and IA(H)2, and poly(1a-IA) in CHCl3 (1.00 mmol L−1).
polymers composed of p-phenylene groups and C8−C24 alkenylene spacers by methathesis polymerization, and the corresponding polymers have alkylene spacers obtained by hydrogenation.13 The polymers with unsaturated spacers show Tg at −51 to −36 °C, and those after hydrogenation undergo the glass transition at higher temperatures (−31 to −8 °C). Low Tg values of the polymers in this study are also attributed to the presence of aliphatic spacers, although low molecular weight polymers need to be taken into consideration. We conducted dynamic viscoelasticity analysis (DMA) of the polymers in order to obtain further insight into the thermal properties, whose results are shown in Figures 7 and 8. The polymer with the bis(dodecyloxy)phenylene and pyromellitic diimide groups, poly(1a-IA-H), showed results close to those of liquid during −10 to 200 °C and weak elasticity at low temperature. This observation is consistent with the low Tg (
