昭和62年8月5日第三種郵便物許可

令和4年12月25日発行（隔月25日発行）

第40巻

第６号

MATERIAL TECHNOLOGY
材料技術

November-December
2022
Vol. 40, No. 6
ISSN 0289-7709
CODEN: MTECFQ

材料技術研究協会
Japan Research Institute ofMaterial Technology
https://www.jrimt.jp

MATERIALTECHNOLOGY
材料技術

VOL. 40, NO. 6
NOVEMBER-DECEMBERCONTENTS＜ARTICLES＞
PREPARATION AND POLYMERIZATION OF PENTAETHOXYDISILOXANE
Iori ABE, Yohei SATO, Ryohei HAYAMI, Kazuki YAMAMOTO, Satoru TSUKADA,
Takahiro GUNJI···················································································50＜報告＞2022 年度

材料技術研究協会討論会報告

討論会委員会 委員長 酒井 秀樹・実行委員長 羽田 宣弘·································57<EDITORIAL NOTE>
編集後記···························································································60

Preparation and polymerization of pentaethoxydisiloxane
Iori ABE 1), Yohei SATO 1), Ryohei HAYAMI 1), Kazuki YAMAMOTO 1),
Satoru TSUKADA 1), and Takahiro GUNJI 1), *Abstract
We previously reported the synthesis of pentaethoxydisiloxane (PEDS) by the oxidation of triethoxysilane(TES) with oxygen gas in the presence of a Rh catalyst. However, the isolate yield of PEDS was low (<7%). Herein, we report a PEDS yield of 62% using a new synthetic method and the characterization of
the PEDS polymer by nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR)
spectroscopy. The PEDS polymer was synthesized by hydrolysis–condensation of PEDS, and this polymer

was composed of linear and branched chains and was the end group of the Q1 unit.

Keywords：Hetero-disiloxane, Polymerization, NMR, FTIR
Received November 24, 2022; accepted February 8, 2023

1) Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science,
2641 Yamazaki, Noda, Chiba 278-8510, Japan*Corresponding author E-mail: gunji@rs.tus.ac.jp50

1. Introduction

polymerized due to insufficient amount of PEDS

Pentaethoxydisiloxane (PEDS) is a hetero-synthesized by the previous method.

siloxane having a hydrido group and can besubstituted by addition reaction with olefins 1). We

2. Experimental section

previously reported that PEDS was synthesized by

2.1 Materials

the oxidation of triethoxysilane (TES) in the

Toluene and tetrahydrofuran (THF) were purified

presence of Rh(PPh3)3Cl catalyst and activatedusing standard methods and stored in activatedmolecular sieves with oxygen gas bubbling 2). This

molecular

reaction proceeded via the formation of silanol (Si–tetraethoxysilaneOH) via the oxidation of the Si–H bond, followed by(TMSCl), and thionyl chloride (SOCl2) werecondensation between Si–OH and Si–OEt. However,purchased from Tokyo Chemical Industry Co. Ltd.

this condensation reaction produces ethanol, and Si–(Japan), and TES and TEOS were purified by

OEt is formed by the reaction between Si–H anddistillation. Ammonium

ethanol (Figure 1). Activated molecular sieves are

dimethylformamide (DMF) were purchased fromnecessary to remove ethanol.

FUJIFILM Wako Pure Chemical Corporation

sieves.

Triethoxysilane(TEOS),(TES),

chlorotrimethylsilane

carbonate

and

N,N-

(Japan). Water was purified using a PURELAB Flex
5 water purification system (ELGA, UK) with aresistivity of ~15 MΩ·cm.
2.2 Measurements
GC analysis was carried out on a GC-390 (GLScience, Japan) packed with an SE-30 capillarycolumn (Agilent, USA) and a TCD detector. Helium
was used as the carrier gas. The column temperature
was programmed as follows: injection temperature
at 250 °C, isothermal state at 80 °C for 2 min, thenheating up to 200 °C at rate of 10 °C min−1, followed
Figure 1 Scheme for oxidation of triethoxysilane. Numbers inparentheses indicate the GC area ratio.

by heating up to 280 °C at rate of 20 °C min−1, andheld at the final temperature of 280 °C for 2 min.
Nuclear magnetic resonance (NMR) spectra were

We found that the side reactions could berecorded on a JEOL Resonance JNM-ECP 300

suppressed when the adsorption rate of the molecular

spectrometer (JEOL, Japan; 1H at 300 MHz, 13C atsieves was faster than the rate of ethoxylation 3).

75 MHz, and 29Si at 60 MHz). Chemical shifts were

However, this reaction is an inefficient andreported in ppm relative to chloroform-d (CDCl3) as

inappropriate synthetic method for PEDS because

the internal standard (for 1H:7.26 ppm and 13C:77.16

the isolated yield of PEDS was 7%. According to the

ppm in residual chloroform) and tetramethylsilane asreaction mechanism, PEDS can be synthesized via

the internal standard (for 29Si:0.00 ppm). For the 29Si

the reaction of isolated triethoxysilanol (TESOL)NMR spectra, Cr(acac)3, as a paramagnetic

with TES. Herein, we report a new synthetic methodrelaxation agent, was added to the samples. Gel

for PEDS. Moreover, we studied the PEDS

permeation chromatography (GPC) was performed

polymerization and its structure, which could not be51

using an HPLC system (LC-6AD, Shimadzu, Japan)

a colorless liquid (yield: 62%).

attached to a PLgel 5 μm Mixed-D column. THF was

1

H NMR: δ = 1.24 (t, J = 7.0 Hz, 9H, CH3 in Q unit),−1

used as the eluent (1 mL min ). RID-10A was used

1.25 (t, J = 6.9 Hz, 6H, CH3 in T unit), 3.86 (q, J =as the detector at 40 °C. The molecular weights were

7.0 Hz, 6H, CH2 in Q unit), 3.87 (q, J = 6.9 Hz, 4H,

calculated based on polystyrene standards. Fourier-CH2 in T unit), 4.35 (s, 1H, Si–H). 13C NMR: δ =transform infrared (FTIR) spectra were recorded on

18.05 (CH3), 18.17 (CH3), 58.27 (CH2), 59.23 (CH2).

an FT-IR spectrophotometer (FT/IR-6100, JASCO,

29

Si NMR: δ = −67.7, −88.4.

Japan) using the neat method, in which the sample
was sandwiched between two KBr crystal disks.

2.5 Polymerization of PEDSPEDS (5.0 g, 17 mmol) and ethanol (25 mL) were

2.3 Preparation of triethoxysilanol (TESOL)

placed in a 100 mL four-necked flask equipped withTESOL was prepared according to literatures 4,5).

nitrogen inlet and outlet tubes and a mechanical

TEOS (26 g, 0.13 mol) was added to a mixture ofstirrer. The mixture was stirred at 200 rpm and thenSOCl2 (14.9 g, 0.13 mol) and DMF (0.13 mL), andcooled in an ice bath for 20 min. Thereafter, conc.

then stirred for 4 h. Chlorotriethoxysilane wasHCl (aq) (0.28 mL), water (0.09 mL), and ethanol (5separated by distillation under reduced pressure (70–mL) were added (HCl/PEDS=0.2, H2O/PEDS=1.0).

72 °C/36 mmHg) and obtained as colorless liquid

The resulting mixture was stirred for 10 min in an ice(yield 59%, GC purity 82%). A solution ofbath and then for 10 min at 22±3 °C. The hydrolysis–

chlorotriethoxysilane (9.9 g, 0.05 mol) and 100 mL

condensation reaction was carried out at 80 °C for 3

THF was added, while stirring under an ice bath, toh under a nitrogen flow of 200 mL min−1. The PEDSa suspension of water (4.5 g, 0.25 mol), (NH4)2CO3

polymer was obtained as a colorless and viscous(28.5 g, 0.25 mol), and THF (250 mL). After stirring

liquid (3.2 g). The average molecular weight (Mw)for 1 h, the precipitate was filtered, and the filtrate

and polydispersity index were 24,000 and 6.8,

was dried over Na2SO4. Thereafter, THF wasrespectively, as calculated by GPC.

evaporated in ice bath under reduced pressure, and
TESOL was separated by distillation under reduced

2.6 Hydrolysis of PEDS followed by addition ofpressure (61 °C/1 mmHg). TESOL was a colorless

TMSClliquid (yield, 62%; GC purity, 82%), but TEOS was

PEDS (1.5 g, 5 mmol) was mixed in ethanol (7.5

contaminated (12%).

mL) in an ice bath for 20 min. Then, conc. HCl (aq)(0.08 mL), water (0.03 mL), and ethanol (1.5 mL)

2.4 Synthesis of PEDS

were added (HCl/PEDS=0.2, H2O/PEDS=1.0). The

TESOL (1.1 g, 6.1 mmol) was added using a

resulting mixture was stirred in an ice bath for 10

dropping funnel to a solution of TES (1.0 g, 6.1

min, followed by the addition of TMSCl (0.64 mL).

mmol) and toluene (3 mL) and stirred at 100 °C.

After stirring, the solvent was evaporated, and a

After 4 hours, PEDS was isolated by distillation

colorless liquid was obtained.

under reduced pressure (104 °C/11 mmHg) to obtain

52

Figure 2 GC traces of the reaction solution of (a) TESOL with TES and (b) TESOL with TEOS at 100 °C for 4 h

the condensation reaction by evaporating the solvent

3. Results and discussion
3.1 Synthesis of PEDS by the reaction of TESOL

5,7,8). The 29Si NMR spectra of PEDS and PEDS

polymers are shown in Figure 3. PEDS displays two

with TES

signals at −67.7 and −88.4 ppm due to T1 unit

A GC chart of the TES and TESOL reaction(HSi(OEt)2OSi(OEt)3)

solutions is shown in Figure 2a. TEOS was observed

and

Q1

unit

(HSi(OEt)2OSi(OEt)3), respectively. PEDS polymer

because TESOL was contaminated with TEOS;

was confirmed by six obvious signals (−68.0, −77.2,

therefore, TES was not completely consumed.

−86.4, −88.9, −96.3, and −104 ppm) and four

However, strong peaks corresponding to PEDS andshoulder signals (−76.0, −84.6, −95.4, and −103

ethanol were observed, indicating that the reactionppm). Because the cyclic form generally has a lower

between TESOL and TES proceeded under neutral

magnetic field than linear and branched chains 9), theconditions. In contrast, Figure 2b shows the GC chart

obvious signals were attributed to linear andof the reaction solution of TEOS with TESOL, andbranched chains, and shoulder signals were assigned

the intensities of ethanol and hexaethoxydisiloxane

to the cyclic form. However, the intensity of the(HEDS) were very weak, indicating that little

shoulder signals was weak, indicating that only areaction occurred between TESOL and TEOS.

small amount of cyclic form was present. The T1 and

TESOL could not be observed because it may haveQ1 units of the PEDS polymer shifted to a slightly

been adsorbed onto the SE-30 capillary column. As

higher magnetic field than those of PEDS. Thisa result, TES is easily attacked by the silanol groupindicates that the T1 and Q1 units are the end groups

and siloxane linkages can be formed even underof the PEDS polymer. The intensity of the T1 unit

neutral conditions because of the low steric

was very weak; hence, the end group of the PEDS

hindrance of Si–H 6).

polymer was mainly the Q1 unit. These attributes are
summarized in Table 1.

3.2 Characterization of PEDS polymer

The FTIR spectra of the PEDS and PEDSThe PEDS polymer was prepared by thepolymers are shown in Figure 4, and the absorptionhydrolysis–condensation reaction of PEDS underbands were attributed with reference to the literature

nitrogen gas flow. Nitrogen gas was introduced to

10,11) and are summarized in Table 2. The position ofremove the hydrochloric acid catalyst and accelerateυSi–H in the PEDS polymer shifted to a higher
53

wavenumber (from 2212 to 2240 cm−1) than that inTable 2 Assignment for FTIR spectra of PEDSs

pristine PEDS, indicating that the condensation

PEDS

PEDS polymer

Assignmenta

reaction proceeded 12,13).

2979, 2931, 2890

2982, 2931, 2896

υCH2, υCH3

2212

2240

υSi–H

1487–1296

1487–1296

δCH2, δCH3

1170

1167

ρCH3

1150–1050

υSi–O–Si

1103, 1081

1103, 1081

υC–O

970

970

υC–C

882

885

ωSi–H

853

υSi–O–Si

796

793

υSi–O–Si

758

755

ρCH2

479

δSi–O–Si

Figure 3 29Si NMR spectra of PEDS and PEDS polymer

Table 1 Assignment for 29Si NMR spectra of PEDSs

710, 634, 612

PEDS
−67.7

−88.4

PEDS polymer

Assignment

482

−68.0

T1

a : stretching, : scissoring, : wagging, : rocking−76.0

Cyclic T2−77.2

Linear T2

The shape of υSi–O–Si at 1150–1050 cm−1

−84.6

Cyclic T3

indicated that the PEDS polymer was not−86.4

Branched T3comprised of ladder-like, cage-like, or strained

−88.9

Q1

cyclic structures 14–16), that is, the PEDS polymer−95.4

Cyclic Q2

was composed of linear, branched, and cyclic−96.3

Linear Q2

structures. However, the absorption band at ~550

−103.0Cyclic Q3

cm−1 due to the cyclotetrasiloxane moiety 17) was−104.0Branched Q3very weak. Thus, the structure of the PEDS polymer
consists mainly of linear and branched chains, whichis consistent with the 29Si NMR results. From theresults of 29Si NMR and FTIR, the PEDS polymer
was composed of mainly linear and branched chainsand had an end group of Q1 unit. Si–H can be
modified by hydrosilylation 1), alkoxylation 18–20),hydroxylation 21), and siloxylation 22,23); hence,
PEDS polymers can be used as precursor polymers
for many functional siloxane polymers and materials,
such as mesoporous silica 24–26).
3.3 Hydrolysis of PEDS
To measure the initial stage of PEDS hydrolysis
reaction, PEDS was hydrolyzed at ~0 °C for 10 min

Figure 4 FTIR spectra of PEDS and PEDS polymer

and silanol was capped with TMSCl. Figure 5 shows54

4. Summarythe 29Si NMR spectra of the hydrolysate. Two signalsof the T2 unit at ~ 75 ppm and two signals of the Q2

We report a new method for the synthesis of PEDS

unit at ~ 96 ppm were confirmed because the signals

via the reaction of TES with TESOL. In the previousnof trimethylsilyl-capped T and Q units appeared atmethod using the oxidation reaction of TES in thea lower magnetic field than that of the condensation

presence of the Rh catalyst, the isolated yield wasof T–T or T–Q 27). The T1 unit disappeared, and the

7%. In comparison, the isolated yield of PEDS by then1

Q unit remained, indicating that the hydrolysis andnew synthetic method was 62%, which wascondensation rates of the T1 unit were faster thanapproximately nine times greater than that obtained1by the previous method. The PEDS polymer was

into the T unit.

prepared by the hydrolysis–condensation reaction of

those of the Q unit. The T unit is mainly transformed
3

The signal pattern of the initial stage of hydrolysis

PEDS under acidic conditions. This polymer isof the PEDS differed from that of the PEDS polymer.

composed of both linear and branched chains.

We consider that the Si–O–Si network of the PEDS

However, the PEDS backbone in this polymer ispolymer was rearranged during the condensation

likely to be partially disintegrated, which isreaction because Si–O–Si bonding is cleaved underconsidered to perform a condensation reaction underacidic conditions

28).

Therefore, we believe thatacidic conditions. Therefore, it may be possible tocondensation reactions using formic acid can be usedsynthesize polymers that retain the PEDS backbone

to obtain polymer-maintained PEDS backbones

by performing condensation reactions under neutral

because formic acid can be easily transformed into

conditions.

formate compounds 29,30). In the future, we will
investigate

thishypothesisbyperforming

Conflict of interesthydrolysis–condensation of PEDS using formic acid.

The authors declare no competing interests.

The changes in the properties due to the polymer
structure will also be investigated.

CRediT authorship contribution statement
Iori Abe: Writing – original draft, visualization,
investigation; Yohei Sato: Writing – original draft;
Ryohei

Hayami:

Writing–

original

draft,

visualization, investigation; Kazuki Yamamoto:Supervision;

SatoruTsukada:Supervision;

Takahiro Gunji: Writing – review and editing,conceptualization, supervision.

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56

2022 年度

202212

材料技術研究協会討論会報告

1

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討論会委員会委員長

酒井 秀樹 （東京理科大学）

討論会実行委員長

羽田 宣弘 （環太平洋大学）

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編集後記
公開が遅れておりました Volume 40 の最終号(2022 年, Volume 40,No.6)
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60

MATERIAL TECHNOLOGY 材料技術
昭和62年8月5日第三種郵便物許可

令和4年12月25日発行（隔月25日発行）

第40巻

第６号

定価2,100円