Ring-opening polymerization of isopropylglycidyl

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Ring-opening polymerization of isopropylglycidyl ether (IPGE) with new catalysts of Ti, Sn, Al-alkoxides and comparison of its reactivity Gamze Yalçın & Asgar Kayan

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Department of Chemistry, Kocaeli University, Kocaeli, 41300, Turkey Version of record first published: 02 Jul 2012

To cite this article: Gamze Yalçın & Asgar Kayan (2012): Ring-opening polymerization of isopropylglycidyl ether (IPGE) with new catalysts of Ti, Sn, Al-alkoxides and comparison of its reactivity, Designed Monomers and Polymers, 15:4, 405-416 To link to this article: http://dx.doi.org/10.1080/1385772X.2012.686693

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Designed Monomers and Polymers Vol. 15, No. 4, July 2012, 405–416

Ring-opening polymerization of isopropylglycidyl ether (IPGE) with new catalysts of Ti, Sn, Al-alkoxides and comparison of its reactivity Gamze Yalçın and Asgar Kayan*

Downloaded by [University of Guelph] at 11:59 17 August 2012

Department of Chemistry, Kocaeli University, Kocaeli 41300, Turkey

The polymerization reactions of isopropylglycidyl ether (IPGE) were carried out by various catalysts potassium hydroxide, potassium tert-butoxide, tetrafluorophthalate aluminum secbutoxide, tetrafluorophthalate tin tert-butoxide, and tetrafluorophthalate–titanium isopropoxide complexes. Tetrafluorophthalate–aluminum, tin, and titanium have been prepared from aluminum sec-butoxide, tin tert-butoxide, and titanium isopropoxide in alcohol and tetrafluorophthalic acid. Poly-IPGE and catalysts were characterized by 1H, 13C NMR, FTIR spectroscopy, elemental analysis, and gel permeation chromatography. IPGE is less reactive toward OH nucleophiles than 3-glycidyloxypropyltrimethoxysilane and propylene oxide. Keywords: polymer; catalyst; synthesis; NMR; ring opening

1. Introduction Ring-opening polymerization of epoxide monomers has been gaining attention in both academic and industrial circles due to its wide range of applications such as production of detergents, nonionic surfactants, washing agents, the heavy metal-free coating, filler, extenders, in drinking water distribution systems, antireflective composition for photoresists, reinforced plastics, adhesives, and polyurethane production process [1–6]. Propylene oxide (PO), styrene oxide (SO), 3-glycidyloxypropyltrimethoxysilane (GPTS), and phenylglycidyl ether (PGE) of cyclic ethers have been polymerized by both anionic and cationic catalysts and also by more selective catalyst system and their products characterized by different spectroscopic techniques [6–13]. As in the mechanism of ring-opening polymerization of PO initiated with porphyrin aluminum chloro complex [9,10], I have recently suggested that the polymerization of GPTS initiated with tetrafluorophthalate zirconium complex proceeds as follows [13]. Although there is some spectroscopic evidence (1H NMR) for the formation of polyisopropylglycidyl ether (IPGE) [14–16], nothing is known about the effect of different catalysts on the epoxide ring-opening and polymerization degree of IPGE in polymerization reactions. The first purpose was to prepare and use new catalysts in the ring-opening polymerization of IPGE. The second purpose of this study was to synthesize and characterize the polymers of IPGE prepared with various catalysts. The third purpose was to see whether the side isopropoxymethyl group (CH2OC3H7) of oxirane will affect both the reactivity toward basic catalysts and the regioselectivity and stereoselectivity of polymerization when compared with other groups such as methyl, phenoxymethyl, and trimethoxysilylpropoxymethyl on epoxides. *Corresponding author. Email: [email protected] ISSN 1568-5551 online Ó 2012 Taylor & Francis http://dx.doi.org/10.1080/1385772X.2012.686693 http://www.tandfonline.com

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2.

G. Yalçın and A. Kayan Experimental

Some syntheses and solvent manipulations were carried out under a nitrogen atmosphere. IPGE (Aldrich), potassium hydroxide reagent (ACS, assay 85% min, GFS Chemicals), potassium tert-butoxide (97%, Alfa Aesar), titanium(IV) isopropoxide (98%, Merck), aluminum (III) sec-butoxide (97%, Alfa Aesar), tin(IV) tert-butoxide (99.9%, Aldrich), and tetrafluorophthalic acid (TFPA) (98%, Alfa Aesar) were used as received. 1 H and 13C{1H}NMR experiments were carried out with a Varian 500 MHz and Bruker 300 MHz Ultra shield TM (5 mm quaternary nuclei probe) spectrometer. Varian 500 NMR operates at proton Larmor frequencies of 500 MHz and carbon frequencies of 125 MHz. Infrared spectra of complexes were recorded on Shimadzu 8201/86601 PC spectrometer. The elemental analyses were carried out on a LECO CHNS-932 elemental analyzer. Gel permeation chromatographic (GPC) analysis was performed at 30 °C on a Shimadzu prominence GPC system equipped with a RID-10A refractive index detector, a LC-20AD solvent delivery unit, a CTO10AS column oven, and a set of two columns, PSS SDV 5 μL 1000 Å and PSS SDV 5 μL 50 Å. Tetrahydrofuran (THF) (HPLC grade) was used as the mobile phase at 1.0 mL/min. The sample concentration was 2 mg/1 mL, and the injection volume was 10 μL. The calibration curve was made with seven polystyrene standards covering the molecular weight range from 162 to 34,300 Da. Glass transition temperature of IPGE polymers was determined with a Perkin Elmer DSC 4000 differential scanning calorimeter. The cooling rate was 5 °C/min. 2.1.

Preparation of [(C6F4(COO)2)2Ti4O4(OiPr)4] TiðOi PrÞ4 þ C6 F4 ðCOOHÞ2 ! ½ðC6 F4 ðCOOÞ2 Þ2 Ti4 O4 ðOi PrÞ4

0.002 mol (0.502 g) TFPA was added to 0.002 mol (0.600 g) titanium(IV) isopropoxide complex in 30 mL isopropanol. The reaction mixture was stirred at room temperature for 2 h. Then, the solvent and volatile fractions were removed from light green solid product under low pressure by vacuum pump. Product was washed again with solvent isopropanol and dried in vacuum. 1H NMR (25 ° C, DMSO, ppm) δ: 1.03–1.05 (d, gem-Me2, OiPr), 3.76 (sept., CH, OiPr). 13C NMR (DMSO, ppm): 163.15 (COO), 143.51 (d, 1JCF = 241.5 Hz, CF, C3, C6, C6F4), 139.67 (d, 1JCF = 254.5 Hz, CF, C4, C5, C6F4), 122.26 (C1, C2, C6F4), 72.52 (OCH), 25.89 (gem-Me2, OiPr). Elemental analysis (C28H28O16F8Ti4, Mw = 963.97 g/mol): Calc. C, 34.9; H, 2.93%. Found: C, 34.8; H, 2.88%. FTIR (KBr, cm1): 1630 (strong, νas CO2), 1585, 1520, 1477, 1418 (strong, νs CO2), 1281, 1124, 1078, 1014, 958, 744.

2.2.

Preparation of [(C6F4(COO)2)2Sn4O5(OtBu)2] SnðOt BuÞ4 þ C6 F4 ðCOOHÞ2 ! ½ðC6 F4 ðCOOÞ2 Þ2 Sn4 O5 ðOt BuÞ2

0.0026 mol (0.6353 g) TFPA was added to 0.0026 mol (1.075 g) tin(IV) tert-butoxide complex in 25 ml THF. The reaction mixture was stirred at room temperature for 2 h. Then, the solvent and volatile fractions were removed from white solid product under low pressure by vacuum pump. Product was washed again with solvent THF and dried in vacuum. 1H NMR (25 °C, CDCl3, ppm) δ: 1.52 (s, CH3 of OtBu). 13C NMR (CDCl3, ppm): 163.10 (COO), 145.04 (d, 1 JCF = 247.6 Hz, CF, C3, C6 of C6F4), 141.60 (d, 1JCF = 250.5 Hz, CF, C4, C5 of C6F4),

Designed Monomers and Polymers

407

118.56 (2JCF = 16.6 Hz, C1, C2 of C6F4), 84.57 (OC, OtBu), 31.7 (CH3, OtBu). Elemental analysis (C24H18O15F8Sn4, Mw = 1173.22 g/mol): Calc. C, 24.57; H, 1.55%. Found: C 24.62%, H, 1.37%. FTIR (KBr, cm1): 1720, 1632 (strong, νas CO2), 1520, 1479, 1394 (strong, νs CO2), 1325, 1252, 1126, 1074, 952, 837, 754, 707. 2.3.

Preparation of [(C6F4(COO)2)2Al4O3(OsBu)2]


AlðOs BuÞ3 þ C6 F4 ðCOOHÞ2 ! ½ðC6 F4 ðCOOÞ2 Þ2 Al4 O3 ðOs BuÞ2 0.002 mol (0.503 g) TFPA was added to 0.002 mol (0.526 g) aluminum(III) sec-butoxide complex in 30 mL sec-butanol. The reaction mixture was stirred at room temperature for 2 h. Then, the solvent and volatile fractions were removed from white solid product under low pressure by vacuum pump. Product was washed again with solvent sec-butanol and dried in vacuum. 1H NMR (25 °C, CDCl3, ppm) δ: 3.50 (m, CH, OsBu), 1.32 (m, CH2, OsBu), 1.03 (d, CH3, OsBu), 0.83 (t, CH3, OsBu). 13C NMR (DMSO-d6, ppm): 161.78 (COO), 143.55 (d, 1 JCF = 249.07 Hz, CF, C3, C6 of C6F4), 139.50 (d, 1JCF = 249.00 Hz, CF, C4, C5 of C6F4), 122.07 (2JCF = 15.85 Hz, C1, C2 of C6F4), 67.62 (OCH2, OsBu), 32.15 (CH2, OsBu), 23.51 (CH3, OsBu), 10.52 (CH3, OsBu). Elemental analysis (C24H18O13F8Al4, Mw = 774.31 g/mol): Calc. C, 37.23; H, 2.34%. Found: C 35.72%, H 2.61%. FTIR (KBr, cm1): 1632 (strong, νas CO2), 1520, 1476, 1431 (strong, νs CO2), 1281, 1129, 1080, 962, 846, 760. 2.4.

Polymerization of IPGE with t-BuOK

The catalyst (20 mg, t-BuOK) was taken in a vial, and 1.2 mL of IPGE was added under nitrogen. The mixture was stirred at two different temperatures (25 and 50 °C) for 1 and 2 days. The conversion of monomer (IPGE) to polymers was 17% for stirring at 25 °C and 84% for 50 °C for 2 days. The following data belong to the stirring at 50 °C and 2 days. 1H NMR (CDCl3, ppm), δ: 3.58–3.50 (m, CH2), 3.49–3.43 (m, CH2OiPr), 3.37–3.32 (m, CH), 1.09–1.07 (t, small, CH3, OiPr), 1.05–1.03 (dd, CH3, OiPr). 13C NMR, (CDCl3, ppm), δ: for CH region: 79.07–78.96–78.84 (CH, triad, ii, is-si, ss), 71.77–71.76 (CH, diad, i, s, CHMe2), 70.19, 69.95–69.85 (CH2, diad, i, s), 68.29–68.20–68.12 (CH2OiPr, triad, ii, is-si, ss), 22.08– 22.03 (doublet, CH3, OiPr), (Figure 1). 2.5. Polymerization of IPGE with KOH The catalyst (15 mg, KOH) was taken in a vial, and 1.2 mL of IPGE was added under nitrogen in dry box. The mixture was stirred at 75 °C for 3 days. The conversion of monomer to polymer was followed by GPC and 1H NMR spectroscopy. 1H NMR (CDCl3, ppm), δ: 3.61–3.57 (m, CH2), 3.54–3.46 (m, CH2O), 3.41–3.37 (m, CH), 1.14–1.11 (t, small, CH3, OiPr), 1.09–1.08 (dd, CH3), (Figure 2). 13C NMR, (CDCl3, ppm), δ: for CH region: 79.25–79.13–79.00 (CH, triad, ii, is-si, ss), 72.23–72.08 (CH, diad, i, s, CHMe2), 70.36, 70.10–69.99 (CH2, diad, i, s), 68.47–68.39–68.29 (CH2OiPr, triad, ii, is-si, ss), 22.28–22.26 (d), 22.24–22.21–22.17(t), 22.00 (s). 2.6.

Polymerization of IPGE with [(C6F4(COO)2)2Ti4O4(OiPr)4]

The catalyst [35 mg, (C6F4(COO)2)2Ti4O4(OiPr)4] was taken in a vial, and 1.2 mL of IPGE was added under nitrogen. The mixture was stirred at 75 °C for 2 and 3 days. 1H NMR


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G. Yalçın and A. Kayan

Figure 1.

13

C DEPT spectrum of polymers of IPGE obtained from polymerization with KOtBu at 50 °C.

Figure 2.

1

H NMR spectrum of polymers of IPGE obtained from polymerization with KOH at 75 °C.


409

(CDCl3, ppm), δ: 3.82 (m, small, CH), 3.75–3.20 (m, CH2, CH2O, OCH), 1.08 (s, CH3). 13C NMR, (125 MHz,CDCl3, ppm), δ: for CH region: 79.21–79.04–78.96 (CH, triad, ii, is-si, ss), 73.02–72.91 (CH, diad, i, s, CHMe2), 72.27–72.12 71.96 (CH2, triad, ii, is-si, ss), 69.17, 68.65–68.55- 68.33–68.23 (CH2OiPr, diad, i, s), 22.12 (s, CH3) (Figure 3). 2.7.

Polymerization of IPGE with [(C6F4(COO)2)2Sn4O5(OtBu)2]


The catalyst [35 mg, (C6F4(COO)2)2Sn4O5(OtBu)2] was taken in a vial, and 1.2 mL of IPGE was added under nitrogen. The mixture was stirred at 75 °C for 2 and 3 days. 1H NMR (CDCl3, ppm), δ: 3.83 (s, broad, CH), 3.75–3.20 (m, CH2, CH2O, OCH), 1.08 (s, CH3), (Fig. 4).13C NMR, (125 MHz, CDCl3, ppm), δ: for CH region: 79.20–79.03–78.95 (CH, triad, ii, is-si, ss), 73.00–72.90 (CH, diad, i, s, CHMe2), 72.28–72.13–71.98 (CH2, triad, ii, is-si, ss), 69.18, 68.53–68.30 (CH2OiPr, diad, i, s), 22.12 (s, CH3). 2.8.

Polymerization of IPGE with [(C6F4(COO)2)2Al4O3(OsBu)2]

The catalyst [35 mg, (C6F4(COO)2)2Al4O3(OsBu)2] was taken in a vial, and 1.2 mL of IPGE was added under nitrogen. The mixture was stirred at 75 °C for 2 and 3 days. 1H NMR (CDCl3, ppm), δ: 3.70–3.20 (m, CH2, CH2O, CH), 1.09–1.08 (s, CH3). 13C NMR, (125 MHz, CDCl3, ppm), δ: for CH region: 79.22–79.10–78.98 (CH, triad, i, is-si, s), 73.01–72.90 (CH, diad, i, s, CHMe2), 72.26–72.13–72.00 (CH2, triad, ii, is-si, ss), 69.18, 68.53–68.30 (CH2OiPr, diad, i, s), 22.12 (s, CH3) (yield: 12%).

Figure 3. 13C NMR spectrum of polymers of IPGE obtained from polymerization with (C6F4(COO)2)2 Ti4O4(OiPr)4 at 75 °C.


410


Figure 4. 1H NMR spectrum of polymers of IPGE obtained from polymerization with (C6F4(COO)2)2 Sn4O5(OtBu)2 at 75 °C.

3.

Results and discussion

Reactions of M(OR)m (M-OR: Ti-OiPr, Sn-OtBu, Al-OsBu, m: 4 for Ti, Sn, m: 3 for Al) with tertafluorophthalic acid in 1:1 molar ratio in alcohol at room temperature gave the products of [(C6F4(COO)2)2Ti4O4(OiPr)4], [(C6F4(COO)2)2Sn4O5(OtBu)2], and [(C6F4(COO)2)2As l4O3(O Bu)2], respectively. In the presence of strong acid like TFPA, some of the alkoxy groups undergo condensation to form oxo group. The amount of oxo group determined by elemental analysis and NMR measurement changes depending on reaction time and temperature. In the FTIR spectrum of tetrafluorophthalate–Ti(IV), Sn(IV), and Al(III) complexes the bands indicate presence of chelating carboxylic groups. The FTIR spectrum of free TFPA exhibits intense bands at 1730–1720, 1636, and 1424 cm–1 corresponding to asymmetrical and symmetrical stretching vibrations of the carboxyl groups. After coordination of tetrafluorophthalate to metal alkoxides, the bands at high wave numbers shift to low wave numbers to approximately, 1630, 1520, 1478, and 1430 cm1. The carboxyl bands appear at 1630 cm1 for νCOOasym and 1430 cm1 for νCOOsym. Tetrafluorophthalate–Sn(IV) complex also includes monodentate carboxylic group at 1720 cm1. This can be related to the large size of tin atom. All of these values are consistent with those detected in a number of carboxylate-metal(IV or III) derivatives [13,15–22]. The 1H NMR spectra of tetrafluorophthalate–Ti, Sn, and Al complexes show the expected peaks and peak multiplicities. For example, 1H NMR spectrum of Ti-complex showed doublets at 1.04 ppm because of gem-dimethyl protons and a septet at 3.76 ppm for CH proton of isopropoxy groups in Ti-complex. The 13C NMR spectra of the metal complexes show shifts for the carboxylate carbons and C1-C2 resonances compared with that of the free tertafluorophthalic acid molecule. The single resonances at δ = 163.15, 163.10, and 161.78 ppm are attributed to the COO– groups in Ti, Sn, and Al complexes, respectively. The chemical shifts



411

and coupling constants given in experimental section are in agreement with reported values [13,20]. Polymer samples obtained from ring-opening polymerization of IPGE were characterized by 1H, 13C NMR, GPC, FTIR, and DSC. 13C DEPT, 13C{1H}, and 1H NMR spectra were obtained at 13C frequencies of 125 MHz and 1H frequencies of 500 and 300 MHz. The 1H NMR assignments of pure IPGE are as follows: CH3: 0.92–0.96(t, OiPr), ring-CH2: 2.35 (1H, dd), CH2: 2.50 (1H, t), ring-CH: 2.89 (m), CH: 3.12–3.16(dd, OiPr), CH2: 3.45 (m, CH2OiPr) ppm. 1H NMR spectrum shows that main change occurs at the CH and CH2 protons of epoxy ring when IPGE is polymerized. The CH and CH2 protons shift to higher values 3.20– 3.83 ppm from 2.35–2.89 ppm. These values are consistent with those of GPTS and PO in the literature [13,23,24]. 1H NMR spectrum of IPGE polymers (prepared with KOH) gives peaks at 3.61–3.57 (m, CH2), 3.54–3.46 (m, CH2OiPr), 3.41–3.37 (m, CH), 1.09–1.08 (dd, CH3, OiPr). The proton NMR spectrum also includes small peaks at 2.35–2.89 ppm for monomer IPGE. The 13C NMR spectrum of pure IPGE shows six resonances which are attributed to the carbon atoms as follows: 21.57, 21.78 (CH3, OiPr), 43.97 (ring-CH2), 50.69 (ring-CH), 68.62 (CH2O), 71.68 (CH, OiPr) ppm. The CH, CH2, and OCH3 carbons of IPGE polymers are easily determined from 13C DEPT spectra. 13C DEPT-135 gives all CH and CH3 in a phase (peaks up) opposite to CH2 (peaks down). 13C NMR spectrum of IPGE polymers includes more peaks than that of pure IPGE. 13C NMR data of IPGE polymers were given in the experimental section. For example, as seen from the 13C NMR data of IPGE polymers prepared with KOtBu catalyst, the regioisomer of –(CHRCH2O)n– was formed. The methine carbon resonances in 13C NMR spectrum at 79.07–78.96–78.84 ppm region appear as three signals readily assignable to the triads (ii, is-si, ss). This is attributed to different stereosequences due to its asymmetric methine carbon. The side propoxymethyl group of IPGE has similar stereoselective effect on stereosequences when compared to the methyl group of PO and trimethoxysilylpropoxymethyl group of GPTS [7,13,23,24]. When KOH and KO-t-Bu are used as catalysts, the reaction pathway leading to polymers formation can be shown in Scheme 1. The strong nucleophiles OH and t-BuO ions attack CHR carbon atom as seen in Scheme 1 (c. 95%). In addition to the main regioregular triads, additional regioregular polymer is possible with small intensity (as seen from 13C NMR spectrum, KOH > [(C6F4 (COO)2)2Ti4O4(OiPr)4] > [(C6F4(COO)2)2Sn4O5(OtBu)2] > [(C6F4(COO)2)2Al4O3 (OsBu)2] catalysts. The reaction pathway leading to polymers formation can be shown in Scheme 2 when tetrafluorophthalate–Ti, Sn, and Al complexes are used as catalysts. Experimental data support that the alkoxide groups bound to metal are active groups to ring opening of epoxide. Catalysts without alkoxide groups prepared at high temperature were not active to ring opening of epoxide. As seen from the 13C NMR data of IPGE polymers prepared with tetrafluorophthalate–Ti complex, both regioisomers are formed but that the major regioisomer –(OCH2CHR)n– predominates by c. 9:1 (or major product 90%) (R: CH2OCHMe2). When both OR and tetrafluorophthalate metal complexes were used as catalysts, there were similarities in region regularity of IPGE polymers. As seen from 13C NMR spectrum (Figure 3), the methine carbon shows three peaks due to triad sensitivity. The higher methine peak at 79.21 ppm corresponds to the isotactic triad as in the literature for poly-PGE [12]. The heterotactic(is-si) triads appear at 79.04 ppm as a sin-


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Scheme 1.


Attacking of R1O to CHR carbon of IPGE.

gle peak because of their close chemical shifts. The peak at 78.96 ppm is attributed to the syndiotactic triad. The main chain methylene carbon appears as three signals which correspond to a triad sensitivity. The peak at 72.27 ppm is attributed to the isotactic triad. The heterotactic(is-si) triads appear at 72.12 ppm as a single peak. The peak at 71.96 ppm is attributed to the syndiotactic triad. The number of methyl peaks (in 1H, 13C NMR spectra) of isopropoxide group bound to glycidyl shows that tetrafluorophthalate-metal catalysts are more stereoselective in polymerization of IPGE. These data suggest that first IPGE attacks to Ti center and then the nucleophile OiPr ion attacks CHR carbon atom in IPGE as seen in Scheme 2. When reaction time is increased from three days to five days, just molecular weight of polymer increases without any change in regio- and stereoselectivity. Tetrafluorophthalate metal complexes produce low molecular weight polymers as seen from Table 1. GPC was also used to determine molecular weight and the molecular weight distribution index of polymers. By varying the reaction time and catalyst, the polymers with different average molecular weights or number average molecular weights were obtained (Figures 5 and 6). Polymers of IPGE prepared with KOtBu by stirring at 50 °C for 2 days, the main peak appeared at weight average molecular weight (Mw) 27,517 Da or number average molecular weight (Mn) 26,778 Da. The ratio of the weight average molecular weight to the number average molecular weight (Mw/Mn) was 1.03. Data for IPGE polymers prepared at different times and temperatures are given in Table 1. As seen from Table 1, polymers prepared at room temperature have lower molecular weight and smaller molecular weight distribution index for



Scheme 2.

413

Attacking of IPGE to Ti center of catalyst tetrafluorophthalate–Ti complex.

KOtBu catalyst. When the temperature increases to 50 °C, the molecular weights and the conversion of monomer to polymer increase. The stereosequence of IPGE polymers prepared with OH and t-BuO was the same for 50 and 75 °C. Polymers of IPGE prepared with tetrafluorophthalate–Ti complex by stirring at 75 °C for 3 days, the main peak appeared at weight average molecular weight (Mw) 2775 Da or number average molecular weight (Mn) 1871 Da. The ratio of the weight average molecular weight to the number average molecular weight (Mw/Mn) was 1.48. There were also small peaks of average molecular weight at 770 and 767 Da (with c. Mw/Mn 1.0). These results indicate that the polymerization has a characteristic of living polymerization. The polymer structure can be further verified by DSC analysis. According to the DSC test, IPGE polymers showed a single glass transition temperature (Tg) below 33 °C. Tg was taken as the midpoint of the glass transition. FTIR studies support the polymerization of IPGE. The monomer of IPGE shows characteristic band at 1255 cm1 (epoxide ring breathing). When IPGE undergoes polymerization,

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Table 1. Data for IPGE polymers obtained from GPC measurements. Time T (°C) (days)


Catalyst KOtBu KOtBu KOtBu

RT 50 50

2 1 2

KOH Tetrafluorophthalate–Ti

75 75

2 3

Tetrafluorophthalate–Sn

75

3

Tetrafluorophthalate–Al

75

3

Conversion (%)

Mw

Mn

Mw/Mn

3989 19,427, 8816 27,517, 11,852, 5642 19,632, 6575 2775, 770,552 2221, 585, 406 647, 423

3115 18,518, 8539 26,778, 11,743, 5439 18,989, 5775 1871, 767,550 1822, 583, 404 647, 421

1.28 1.05, 1.03 1.03, 1.01, 1.04

17 63 84

1.03, 1.14 1.48, 1.00, 1.00 1.22, 1.00, 1.01 1.02, 1.00

64 44

Figure 5.

GPC of IPGE polymers prepared at 50 °C with KOtBu.

Figure 6.

GPC of IPGE polymers prepared at 75 °C with (C6F4(COO)2)2Ti4O4(OiPr)4.

31 12

the peak at 1255 cm1 disappears in the FTIR spectrum. This disappearance supports the fact that the epoxy ring of IPGE undergoes a ring-opening reaction [13,25]. These all data support the polymerization of IPGE.


415

The reactivity of epoxides towards OH and OtBu ions is investigated by both 1H NMR spectroscopy and GPC. The polymerization rate of epoxides decreases in the order of PO > GPTS > IPGE. In basic condition (OH), PO and GPTS undergoes the ring-opening polymerization reactions at room temperature for one day with high conversion 95 and 35%, respectively. However, IPGE does not undergo the ring-opening reaction with OH ions at room temperature. IPGE undergoes the ring-opening polymerization at 75 °C for 2 days with just 64% conversion. This inertness towards basic catalysts can be attributed to both electronic and steric effects of the side isopropoxymethyl group of isopropylglycidyl.


4.

Conclusion

The five catalysts used in this study are effective for the polymerization of IPGE and have somewhat different influence on the selective synthesis of polymers. Mainly one regioisomer is formed due to the ring opening of epoxide from CHR–O bond. The structures of polymers were characterized by NMR, FTIR, GPC, and DSC analysis. The side isopropoxymethyl group of IPGE has similar stereoselective effect on stereosequences when compared to the methyl group of PO. Isotactic, iso/syn-tactic, and syndiotactic polymers are obtained. As seen from 1H- and 13C NMR spectra and experimental data, there are less peaks in methyl (OCHMe2) region when tetrafluorophthalate metal catalysts were used as catalysts. This is evidence that tetrafluorophthalate-metal catalysts are somewhat more stereoselective in polymerization of IPGE. The polymerization rate of IPGE decreases in the order of KO-t-Bu > KOH > [(C6F4(COO)2)2Ti4O4(OiPr)4] > [(C6F4(COO)2)2Sn4O5(OtBu)2] > [(C6F4(COO)2)2Al4O3(OsBu)2] catalysts. When tetrafluorophthalate–Al complex was used as catalyst, slow polymerization was performed and lower molecular weight polymers were obtained. GPC measurements show that the polymerization has a characteristic of living polymerization with tetrafluorophthalate metal catalysts. Low molecular weight polymers of IPGE were prepared by using tetrafluorophthalate-metal catalysts. The polymerization rate of epoxides decreases in the order of PO > GPTS > IPGE. Acknowledgement This work was supported by the research foundation of Kocaeli University (Project No: 2009/034).

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