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Article

A Complexed Initiating System AlCl3·Phenetole/TiCl4·H2O with Dominant Synergistic Effect for Efficient Synthesis of High Molecular Weight Polyisobutylene

by
Yulong Jin
1,
Liang Chen
2,
Xing Guo
2,
Linfeng Xu
2,
Zhihua Zhu
2,
Zhen Liu
2,
Ruihua Cheng
2 and
Boping Liu
1,*
1
College of Materials and Energy, South China Agricultural University, Wushan Road 483, Guangzhou 510630, China
2
State Key Laboratory of Chemical Engineering, East China University of Science and Technology, Meilong Road 130, Shanghai 200237, China
*
Author to whom correspondence should be addressed.
Polymers 2019, 11(12), 2121; https://doi.org/10.3390/polym11122121
Submission received: 17 October 2019 / Revised: 9 December 2019 / Accepted: 11 December 2019 / Published: 17 December 2019
(This article belongs to the Section Polymer Chemistry)
Browse Figures
Versions Notes

Abstract

:
A complexed initiating system AlCl3·phenetole/TiCl4·H2O was prepared by simply compounding AlCl3/phenetole and TiCl4/H2O and used for cationic polymerization of isobutylene. It was found AlCl3·phenetole/TiCl4·H2O exhibited activities 1.2–3 times higher than those of AlCl3/phenetole, and more than an order of magnitude higher than those of TiCl4/H2O, which indicated a notable synergistic effect produced in the complexed system. In addition, due to the higher activity of AlCl3·phenetole/TiCl4·H2O, lower coinitiator concentration and polymerization temperature, as well as higher monomer concentration were more favored for this complexed initiating system to produce polyisobutylene (PIB) with reasonable molecular weight (Mw) and molecular weight distribution (MWD). Furthermore, high molecular weight polyisobutylene (HPIB) with Mw = 1–3 × 105 g·mol−1 could be successfully produced by the complexed catalyst system at Tp = −60 to −40 °C. As a whole, the high activity as well as the simple preparation procedures of the complexed initiating system offer us a unique approach for the production of HPIB with improved efficiency.

Graphical Abstract

1. Introduction

High molecular weight polyisobutylene (HPIB), which owns viscosity average molecular weight (Mv) higher than 105 g·mol−1, is one of the most unusual polymers and exhibits numerous excellent properties such as extremely low gas permeability, outstanding thermal stability and low fragility [1,2]. Thus it has been applied in the manufacture of sealant, automotive, medical equipment and so forth [3]. Commercially, HPIB is produced with Lewis acid based initiating systems through the cationic polymerization of isobutylene (IB), and polymerization temperature (Tp) as low as −100 °C is necessary to depress the chain transfer or termination reaction and achieve high molecular weight (Mw) polymers [4,5,6]. However, it is obvious that such a low Tp is critical to both energy and equipment costs. Therefore, developing novel initiating systems and manufacture processes for the synthesis of HPIB at elevated Tp is significant.
The novel organometallic catalysts were reported to have an advantage over the synthesis of HPIB [7]. For examples, in the presence of B(C6F5)3 and zirconocenes, Bochmann et al. found polyisobutylene (PIB) with Mw higher than 106 g·mol−1 could be obtained at Tp closed to −70 °C [8]. Jörg et al. reported a dicationic zirconocene for the synthesis of HPIB with Mw higher than 3 × 105 g·mol−1 at Tp below −50 °C [9]. Baird et al. reported that HPIB with Mw =1–6 × 105 g·mol−1 could be produced at Tp = −50 to −10 °C by a half-titanocene coordinated with B(C6F5)3 [10]. It is generally recognized that the weakly coordinating anions (WCAs) such as B(C6F5)3 is indispensable for the organometallic catalysts, as the WCAs act as stabilizer to the active sites and retard the chain transfer reaction [11]. However, much attention has still been paid on the conventional Lewis acid systems both in the academic and industrial fields, as the synthetic routes for these organometallic catalysts are much more complicated, and the cost is also relatively higher. [12]. On the other hand, HPIB could also be produced at elevated Tp with Lewis acid initiating systems, if proper reaction conditions are chosen. Particularly, the AlCl3-based initiating systems, which are widely investigated in both academy and industry for the production of PIB, butyl rubber and other cationic polymers, are among the most favored candidates for the synthesis of HPIB because of the low price, low dosage and high activity [3,13,14,15,16,17,18,19,20]. Lu and coworkers took advantage of the microflow reaction system in perfect mixing and heat transfer performances, as well as narrow residence time distribution, thus a reaction system with enhanced homogeneity and controllability could be created, and PIB with weight-average molecular weight (Mw) higher than 1 × 105 g·mol−1 was produced by AlCl3/H2O at Tp = −30 to −10 °C [21]. Csihony et al. reported a novel initiating system of Lewis acid anion Al2Cl7− trapped in micelles consisting of functionalized low molecular weight PIB. The activity of the system was high enough that HPIB with Mw = 1.7–9 × 105 g·mol−1 and molecular weight distribution (MWD) = 13–47 could be produced at Tp = −76 °C [2]. Wu et al. prepared a series of AlCl3/H2O/ED (ED = electron donor = methyl benzoate, ethyl benzoate, and methyl acrylate) initiating systems. It was found that in the presence of EDs, the Mw of the PIB could reach to 6–8 × 105 g·mol−1 at Tp= −80 to −70 °C, which was even higher than that produced by AlCl3/H2O at Tp = −100 °C [3,22]. Later on, the same group reported another novel initiating system of AlCl3/H2O/veratrole, and HPIB with Mw higher than 1 × 106 g·mol−1 could be synthesized at Tp = −80 °C. It was argued that the EDs were able to interact with the active centers and affect the nucleophilicity and polarity of the microsurroundings around the active centers. As a consequence, the cationic polymerization proceeded in a more controllable way, and side reactions such as chain transfer and termination were depressed, but the propagation rate mostly declined with the increased concentration of EDs [23]. Kostjuk and coworkers found H2O/iBu2AlCl/toluene was able to afford PIB with high Mw at Tp = −20 °C because of the weak basicity of toluene, which would help to stabilize the active species. While for iBuAlCl2 with stronger Lewis acidity, additional ether was needed to suppress side reactions and obtain HPIBs [24]. The same group also disclosed that alkoxy aluminum chlorides-based systems H2O/(RO)0.8+nAlCl2.2−n/n-hexane (R = Bu, Hex or iPr; n = 0–0.4) could produce PIBs with low to medium Mw and relatively narrower MWD. It was found the oxygen in the coinitiator played a key role as electron donor to stabilize the active species, which would retard the isomerization of the macrocation and chain scission and benefit the synthesis of high Mw polymers. Therefore, PIBs with Mw up to 1.2 × 105 g·mol−1 could be produced at elevated Tp = −20 to 20 °C [25].
Recently, an endeavor was made in our group to make HPIB with AlCl3/ROH (R = H, Me, Et, Bu, tBu and Ph) or AlCl3/ether (ether = diethyl ether, butyl ether, anisole and phenetole) initiating systems as well, and HPIB with Mw > 1 × 105 g·mol−1 could be generally produced at relatively elevated Tp = −60 °C. Particularly, AlCl3/phenetole showed the highest efficiency for the synthesis of HPIB among these systems [26]. More recently, a novel complexed system consisting of BF3·EtOH/TiCl4·H2O was reported in our group, and remarkable synergistic effect in its catalytic efficiency could be observed due to this complexation [27]. However, it should be noted that BF3 is highly toxic and environmental unfriendly. Therefore, in this contribution, we tried to make use of AlCl3, which is relatively greener and more economical than BF3, to give another complexed initiating system AlCl3·phenetole/TiCl4·H2O, aiming to produce HPIB with improved efficiency.

2. Materials and Methods

2.1. Raw Material

Isobutylene (Wetry Standard Gas (Shanghai) Co., Ltd., 99.80%, Shanghai, China), anhydrous AlCl3 (Shanghai Aladdin Bio-Chem Technology Co., LTD, 99%, Shanghai, China), TiCl4 (Lingfeng Chemical Co., Ltd., 99%, Shanghai, China) and Phenetole (Shanghai Aladdin Bio-Chem Technology Co., LTD, 99%, Shanghai, China) were used as received. CH2Cl2 (Lingfeng Chemical Co., Ltd., 99%, Shanghai, China) was distilled over CaH2 under the atmosphere of N2 for more than 6 h before use. N2 (Wetry Standard Gas (Shanghai) Co., Ltd., 99.999%, Shanghai, China) was further purified by passing through two columns packed with 4A and silver molecular sieves, respectively.

2.2. Catalyst Preparation and Polymerization

All the polymerizations were implemented in three-necked flasks (ca. 250 mL) under the atmosphere of N2. Standard Schlenk technique was applied to avoid the introduction of air into the reaction system. The isobutylene (IB) gas was firstly liquefied by being introduced to a three-necked flask prechilled in a cooler at the target Tp, and a certain amount of CH2Cl2 was transferred to the flask by a syringe to get the monomer solution. Afterwards, in a glove box under N2 atmosphere, a certain amount of AlCl3 powder was weighted and sealed in a glass tube. To make the solution of the complexed catalyst, the powder was introduced to another three-necked flask and flushed by CH2Cl2, then phenetole, TiCl4 and H2O were sequentially injected into the flask by syringes. Subsequently, both the monomer and catalyst solutions were kept at Tp for at least half an hour. To start polymerization, the catalyst solution was transferred to the monomer solution, and then the reaction system was magnetically stirred and kept for a scheduled time. Subsequently, about 2 mL NaOH/ethanol mixture was poured into the reactor to terminate the polymerization process. The quenched mixture was separated from the solvent by vacuum filtration and washed by deionized water and EtOH three times, respectively. Afterwards, it was dried in vacuum at 40 °C overnight, and the product was attained and weighted. Activities = m(PIB)/(ncat·t) were calculated to compare the efficiencies of these catalysts, where m(PIB) was the weight of the obtained polymers in kilograms, ncat was the amount of the added AlCl3 and TiCl4 in molar number, and t was the reaction time in hour.

2.3. Polymer Characterization

The weight average molecular weight (Mw) and MWD (Mw/Mn) of the obtained PIBs were characterized by gel permeation chromatography (GPC, Waters-1515) combined with two Mixed-C columns. Typically, 10 mg PIB was dissolved in 10 mL tetrahydrofuran (THF) to make polymer solutions with a concentration of 1mg·mL−1, which was then measured at 35 °C at a flow rate of 1.0 mL·min−1. The columns were calibrated by polystyrene standards with narrow MWD.

3. Results and Discussion

3.1. Effect of Coinitiator Concentration

The effect of coinitiator concentration on the polymerization behaviors of reference and complexed catalysts was investigated, and the results were listed in Table 1. At coinitiator concentration lower than 2.5 mmol·L−1, it was obviously for both catalysts that the monomer conversions were enhanced with the increasing catalyst concentration, but to achieve a parallel conversion, lower catalyst concentration was needed for the complexed one, which implied the higher efficiency of the complexed catalyst. It could also be directly reflected by the Δ value in Table 1, showing that the activities of AlCl3·phenetole/TiCl4·H2O were 2–3 times higher than those of AlCl3/phenetole at identical reaction conditions. When the concentration of coinitiator was lower than 1 mmol·L−1, no polymer could be detected for the AlCl3/phenetole system, probably due to the comparable trace concentration of impurity to that of the active sites [28]. However, for the complexed catalyst, a monomer conversion higher than 30% could still be obtained at this low coinitiator concentration. With respect to polymer products, monomodal HPIB with Mw higher than 2 × 105 g·mol−1 and MWD = 2–4 could be produced with both catalysts at low concentration, but the complexed catalyst system was apt to produce PIB with lower Mw and broader MWD when compared with AlCl3/phenetole, as the high polymerization activity made the process control more difficult. When the concentration of coinitiator further increased to higher than 2.5 mmol·L−1, the efficiencies between the two catalyst systems were indistinct.
In addition, the Mw of the PIB decreased and multimodal MWD could be observed (see Figure 1). It was likely that active species with distinct kinetic characteristics existed at high complex concentration. When looking into the GPC curves about the polymers produced by the catalysts before and after complexation together (see Figure 2), it was found the curve of the PIB made by AlCl3·phenetole/TiCl4·H2O was analogous to that by AlCl3/phenetole at low catalyst concentration. While it tended to be the combination of those by AlCl3/phenetole and TiCl4/H2O at high catalyst concentration. However, it was not the result of separate working of the two reference catalysts. Since such a situation would bring about bimodal but not multimodal MWD, and the activities of the complexed catalyst were also difficult to get close to or even higher than those of AlCl3/phenetole, if we consider the much lower efficiency of TiCl4/H2O (see Figures S1–S4 in Supporting Information). Another possibility for the decreased Mw and broadened MWD was presumably owing to the monomer starvation, which would lead to intensified side reactions like chain transfer and termination [29]. Moreover, chain scission should be taken into account as well, because it got more importantly under monomer starvation and was reported to be frequent in the AlCl3-based system for cationic polymerization [15,30]. This could also be directly reflected by the severely decreased Mn when higher catalyst concentration was used. It indicated that low coinitiator concentration is more favored for both initiating systems, specifically for AlCl3·phenetole/TiCl4·H2O because of its higher activity. It preliminarily indicated that an obvious synergistic effect was also produced in the complexed catalyst as that discovered in BF3·EtOH/TiCl4·H2O [27]. To further ensure this synergy, several control experiments with initiating systems consisting of two or three components were also investigated (see Run 11–16 in Table 1). It could be seen that the three components catalysts, as well as 1TiCl4·1phenetole showed very low or even no activities, while 1TiCl4·1H2O and 1AlCl3·1H2O exhibited moderate activities of less than 5 kg PIB·mol−1TiCl4·h−1 and 80 kg PIB·mol−1AlCl3·h−1, respectively. However, under the similar reaction conditions, 1AlCl3·1phenetole/1TiCl4·1H2O gave activities of more than 130 kg PIB·mol−1(AlCl3+TiCl4)·h−1 and presented an obvious synergistic effect. Such a synergistic effect is very interesting, but was difficult to be illustrated at present. Marek and coworkers also found a similar synergistic effect in mixture consisting of two types of Lewis acids for IB polymerization in the absence of initiators, and it was proposed to result from the formation of very active ion pair due to the inter-ionization between the two Lewis acids with different acidity. However, as a certain amount of H2O and phenetole was added in our case, making the existence of a large amount of free Lewis acid unlikely, thus the inter-ionization mechanism was almost impossible. In addition, this synergistic effect could also originate from the modification of the counterion by TiCl4, improving the stability of the growing species for IB insertion [31,32,33]. Nevertheless, deeper investigation is still needed to uncover the mechanism behind.

3.2. Effect of Reaction Temperature

Reaction temperature (Tp) is one of the most important factors in the regulation of catalysis behaviors for cationic polymerization. Thus the effect of reaction temperature was also investigated at Tp = −40 to −60 °C commonly used for the synthesis of PIB (see Table 2). Primarily, it could be seen that the activities of the complexed catalyst were about 1.5–3 times higher than those of the uncomplexed ones under the investigated Tp. Additionally, it was conspicuous that both the monomer conversion and activities of the catalysts went up with increasing Tp, which were contrary to the results mostly reported for cationic polymerization that active sites collapsed more easily at higher Tp, and the conversion was kept almost the same or turned down consequently [5,13,34,35]. However, such a deviation was also disclosed elsewhere [9,28]. It was proposed the tightness of the initiator/coinitiator complex got strengthened at lower Tp. Consequently, the concentration of the free Lewis acids, which play a role as coinitiator for cationic polymerization got lower as well [36]. It could also be partially attributed to the faster generation of active sites in comparison to their decay at higher Tp for both initiating systems. In addition, the viscosity of the reaction system got higher at lower Tp, and it could be more severe in the system for HPIB production, as gel-like PIB with relatively high Mw was generally produced and suspended in the solvent. This would inhibit the smooth going of heat and mass transfer processes, and also improve the possibility of the mechanical occlusion of catalysts by polymer and impair the efficiency of the catalysts [21]. While high Tp would help to create more homogeneous reaction conditions by improving the dissolubility of the polymer. Pertaining to the produced HPIB, the Mw decreased monotonously with increasing Tp, as the chain transfer reaction is more sensitive to temperature changes than chain propagation. The MWD of the HPIB also got slightly narrower at higher Tp. It is most likely that the initiation and chain transfer processes became more competent, while the apparent rate constant for chain propagation was kept almost the same at higher Tp [37,38]. In addition, the more homogeneous reaction conditions at increasing Tp should be taken into account as well. However, an exception was seen at run No 3 and 6 in Table 2, where an increase in MWD was observed. This could be possibly caused by chain scission during polymerization, which was exhibited by the additional low Mw tail in the GPC curves of the polymers (see Figure 3). In comparison to AlCl3/phenetole, the complexed catalyst still tended to produce HPIB with lower Mw and broader MWD, which indicated more dominant side reactions such as chain transfer, termination and scission in the latter initiating system. Moreover, with increasing Tp, a smaller difference in activities between the two systems could be observed, indicating the active sites in the complexed one were more sensitive to temperature and more frequently terminated at higher Tp. It implies the synergistic effect demonstrated in the complexed system not only improves the catalytic efficiency greatly but also poses a challenge to the process controllability of the polymerization reaction. Therefore, lower Tp seemed to be more crucial to AlCl3·phenetole/TiCl4·H2O than AlCl3/phenetole. However, as a whole, HPIB with Mw = 1–2.8 × 105 g·mol−1 and MWD = 2.8–4.1 could be produced with both initiating systems.

3.3. Effect of Monomer Concentration

High monomer concentration ([IB]) is always desired in industry to save the cost, if high conversion could be achieved at the same time. The effect of [IB] on the polymerization behaviors of both initiating systems is shown in Table 3. With regarding to AlCl3/phenetole, the monomer conversion decreased from 70% to 15% when [IB] increased from 2.4 to 5.1 mol·L−1, and the activity also followed the same trend. This decline was possibly derived from the decreasing concentration of the polar solvent CH2Cl2 caused by the increasing [IB], as an active ion pair in AlCl3/phenetole were more likely generated in more polar conditions (see Figure S5). For the complexed catalyst, the monomer conversion was kept at about 90% when [IB] increased from 2.4 to 4 mol·L−1, but obvious drop could also be observed when [IB] increased further. It implies a wider range of applicable [IB] for AlCl3/phenetole/TiCl4·H2O. In addition, the activities of the complexed one were still kept 1.2–2.3 times higher than those of the uncomplexed one. With respect to the produced polymers, the Mw increased with the increasing [IB], as chain propagation was more favored than transfer at higher [IB], and HPIB with Mw = 1.5–3 × 105 g·mol−1 could be generally produced. However, when compared with AlCl3/phenetole, the complexed catalyst was more likely to produce polymer with lower Mw and much broader MWD at the same reaction conditions, and this trend was more distinct at lower [IB]. Again, it is possibly due to the monomer starved condition met in the complexed system, as the high monomer conversion at low [IB] would result in more serious chain scission, which could bring about lowered Mw and broadened MWD [15]. Meanwhile, the polarity of the reaction environment was enhanced at lower [IB], which would facilitate the generation of active sites with stronger cationicity and result in more intensified side reactions [35].

3.4. Effect of Polymerization Time

The polymerization behaviors of the catalysts are likely to change with polymerization time (tp), as the composition of the reaction system is very complex and would vary with time as well. Thus tp in the range of 1–30 min was investigated, and the results are given in Table 4. It is evident that the monomer conversion got higher with longer tp. However, the initial activity was so high that reasonable conversion higher than 50% could be achieved within 1 min, and 90% monomer could be consumed in 5 min. The activities of both catalysts dropped off monotonously over tp, as the concentration of the active sites was higher and the reaction conditions were more homogeneous at the early stage. While the complexed catalyst was still more active than the uncomplexed one and showed activities about 1.2–1.7 times higher under the investigated conditions. In addition, the Mw of the obtained PIB decreased and the MWD got broader, as the tp lasted longer. This could be ascribed to chain scission as the reaction went on, and this reaction became more serious after 5 min, as the monomer conversion went up to a level higher than 90% and gave rise to monomer starvation, which would result in much broader MWD and a stronger reduction of Mn. However, within the first 3–5 min, the Mw was kept high, and HPIB with Mw = 2–3 × 105 g·mol−1 could be produced employing both catalysts, while the MWD was also kept relatively narrow. It indicates that tp equals to 3–5 min is quite adequate to get a satisfactory monomer conversion for the synthesis of HPIB. This also implied that AlCl3·phenetole/TiCl4·H2O exhibited superior efficiency to the recently discovered BF3·EtOH/TiCl4·H2O, as the former one generally showed much higher activities than the latter one, and a much shorter tp was needed for AlCl3·phenetole/TiCl4·H2O to achieve a sufficient monomer conversion under similar reaction conditions [27].

4. Conclusion

By simply compounding the high efficient AlCl3/phenetole for HPIB and the low efficient TiCl4/H2O for HPIB or MPIB, a novel complexed initiating system consisting of AlCl3·phenetole/TiCl4·H2O was successfully prepared. The contrast studies that were carried out between AlCl3·phenetole/TiCl4·H2O and AlCl3/phenetole clearly showed that a notable synergistic effect was produced in the complexed catalyst, as the activities of the complexed system were generally 1.2–3 times higher than those of the AlCl3/phenetole under various reaction conditions. Hence, for the complexed catalyst system, even with very low coinitiator concentration (2–5 mmol·L−1) and relatively high monomer concentration (ca. 4 mol·L−1), a satisfactory monomer conversion higher than 90% could be generally reached within 5 min. In addition, the very high activity of AlCl3·phenetole/TiCl4·H2O due to the synergistic effect made lower coinitiator concentration and polymerization temperature, as well as higher monomer concentration to be more favored for this complexed initiating system to produce PIBs with reasonable Mw and MWD. Moreover, the complexed catalyst also took advantage of AlCl3/phenetole in the production of HPIB, and HPIB with Mw = 1–3 × 105 g·mol−1 could be synthesized under the investigated conditions. It also indicated that AlCl3·phenetole/TiCl4·H2O showed an enhanced competence in producing HPIB when compared with BF3·EtOH/TiCl4·H2O, as PIB with Mw = 0.8–2.2 × 105 g·mol−1 could be produced by the latter system as a whole. Generally, the high activity as well as the simple preparation procedures of the complexed catalyst offer us a unique method for the production of HPIB with improved efficiency.

Supplementary Materials

The following are available online at https://www.mdpi.com/2073-4360/11/12/2121/s1, Figure S1: The effect of solvent polarity on TiCl4/H2O for IB polymerization ([IB] = 2.9 mol·L−1; [H2O] = 20 mmol·L−1; [TiCl4] = 30 mmol·L−1; tp=30 min; Tp = −60 °C.); Figure S2: The effect of Tp on TiCl4/H2O for IB polymerization ([IB] = 2.9 mol·L−1; [H2O] = 20 mmol·L−1; [TiCl4] = 30 mmol·L−1; 60 mL C2H2Cl2;40 mL n-hexane; tp = 30 min); Figure S3: The effect of [H2O] and [TiCl4] on IB polymerization ((a) [TiCl4] = 50 mmol·L−1; (b) [H2O] = 40 mmol·L−1; (c) [TiCl4] = 4.56 mmol·L−1; Other conditions: [IB] = 2.9 mol·L−1; 60 mL C2H2Cl2; 40 mL n-hexane; tp = 30 min; Tp = −60 °C.); Figure S4: The effect of monomer concentration on TiCl4/H2O for IB polymerization ([H2O] = 30 mmol·L−1; [TiCl4] = 20 mmol·L−1; 60 mL C2H2Cl2; 40 mL n-hexane; tp = 30 min; Tp = −60 °C); Figure S5: The effect of solvent polarity on monomer conversion with AlCl3/phenetole initiating system ([IB] = 4 mol·L−1; Vdichloromethane + Vn-hexane = 100 mL; Tp = −60 °C; tp = 30 min; [AlCl3]/[phenetole] = 1/1).

Author Contributions

L.C., L.X. and X.G. planned and conducted the experiments. Y.J. and L.C. analyzed the data and prepared the manuscript. Y.J., Z.Z., Z.L., R.C. and B.L. discussed, reviewed and edited the manuscript.

Funding

This research was funded by Wanhua Chemical (Project No: A100-81404).

Conflicts of Interest

The authors declare no conflict of interest.

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Polymers 11 02121 g001 550
Figure 1. The gel permeation chromatography (GPC) curves of the PIB produced by (A) AlCl3/phenetole and (B) AlCl3·phenetole /TiCl4·H2O at various [AlCl3 + TiCl4] concentrations. The other reaction conditions are listed in Table 1.
Figure 1. The gel permeation chromatography (GPC) curves of the PIB produced by (A) AlCl3/phenetole and (B) AlCl3·phenetole /TiCl4·H2O at various [AlCl3 + TiCl4] concentrations. The other reaction conditions are listed in Table 1.
Polymers 11 02121 g001
Polymers 11 02121 g002 550
Figure 2. The GPC curves of PIB produced by AlCl3/phenetole, TiCl4/H2O and AlCl3·phenetole/TiCl4·H2O, (A) the GPC curves of PIB produced from run 3, 4 and 11 in Table 1; (B) the GPC curves of PIB produced from run 5, 6 and 11 in Table 1 and (C) the GPC curves of PIB produced from run 7, 8 and 11 in Table 1.
Figure 2. The GPC curves of PIB produced by AlCl3/phenetole, TiCl4/H2O and AlCl3·phenetole/TiCl4·H2O, (A) the GPC curves of PIB produced from run 3, 4 and 11 in Table 1; (B) the GPC curves of PIB produced from run 5, 6 and 11 in Table 1 and (C) the GPC curves of PIB produced from run 7, 8 and 11 in Table 1.
Polymers 11 02121 g002
Polymers 11 02121 g003 550
Figure 3. The GPC curves of the PIB produced by (A) AlCl3/phenetole and (B) AlCl3·phenetole/ TiCl4·H2O at different Tp. The other reaction conditions are listed in Table 2.
Figure 3. The GPC curves of the PIB produced by (A) AlCl3/phenetole and (B) AlCl3·phenetole/ TiCl4·H2O at different Tp. The other reaction conditions are listed in Table 2.
Polymers 11 02121 g003
Table
Table 1. Effect of coinitiator concentration on the polymerization results a.
Table 1. Effect of coinitiator concentration on the polymerization results a.
NoCatalysts[AlCl3 + TiCl4]Conv.Act. cMw dMn dMWDΔ e
(mmol·L−1)(%)
11AlCl3·1phenetole0.840-----
21AlCl3·1phenetole/1TiCl4·1H2O0.8434.9186.1420.895.503.8-
31AlCl3·1phenetole1.6716.042.6735.7814.312.51
41AlCl3·1phenetole/1TiCl4·1H2O1.6753.0141.3420.885.094.13.31
51AlCl3·1phenetole2.5140.572.0028.867.593.81
61AlCl3·1phenetole/1TiCl4·1H2O2.5195.0168.9020.030.9620.92.35
71AlCl3·1phenetole3.35100133.3420.425.243.91
81AlCl3·1phenetole/1TiCl4·1H2O3.3598.7131.6114.370.9814.70.99
91AlCl3·1phenetole4.19100106.6712.200.2646.1-
101AlCl3·1phenetole/1TiCl4·1H2O5.0297.186.3212.870.6719.2-
11 b1TiCl4·1H2O50.0071.54.866.411.783.6-
121AlCl3·1H2O3.3559.879.7621.213.985.3-
131TiCl4·1phenetole1.67N.D fN.D fN.D fN.D fN.D f-
141AlCl3·1phenetole·1H2O1.670.61.47----
151TiCl4·1phenetole·1H2O1.670.40.90----
161AlCl3·2phenetole/1TiCl41.670.10.21----
a For each catalyst, the molar ratio of the components is equal to that of the number in front of each component. 100 mL C2H2Cl2, Tp = −60 °C, tp = 30 min, [IB] = 4 mol·L−1; b high [TiCl4] was necessary to achieve reasonable polymerization rate (see Figure S3 in Supporting Information), [IB] = 2.9 mol·L−1; c activity, kg PIB·mol−1(AlCl3+TiCl4)·h−1; d (×104 g·mol−1); e Δ = activity(complexed catalyst)/activity(reference catalyst), where both catalysts contained the same coinitiator concentration. f Not detected.
Table
Table 2. Effect of reaction temperature on the polymerization results a.
Table 2. Effect of reaction temperature on the polymerization results a.
NoCoinitiatorTpConv.Act. dMwMnMWDΔ e
(°C)(%)(×104 g·mol−1)(×104 g·mol−1)
1 bAlCl3−6040.572.0728.867.593.81
2 cAlCl3/TiCl4−6053.0140.9120.885.094.12.96
3 bAlCl3−5061.0108.5522.805.704.01
4 cAlCl3/TiCl4−5088.8236.1013.724.043.42.17
5 bAlCl3−4098.0174.4012.704.542.81
6 cAlCl3/TiCl4−4097.2258.4310.032.514.01.48
a [IB] = 4 mol·L−1; 100 mL C2H2Cl2; tp = 30 min; b [AlCl3] = 2.51 mmol·L−1, [AlCl3]/[phenetole] = 1/1; c [AlCl3] = 0.84 mmol·L−1, [AlCl3]/[TiCl4]/[phenetole]/[H2O] = 1/1/1/1; d activity, kg PIB·mol−1(AlCl3 + TiCl4)·h−1; e Δ = activity(complexed catalyst)/activity(reference catalyst), where both the catalysts reacted at the same Tp.
Table
Table 3. Effect of monomer concentration on the polymerization results a.
Table 3. Effect of monomer concentration on the polymerization results a.
NoCoinitiator[IB]Conv.Act. dMwMnMWDΔ e
(mol·L−1)(%)(×104 g·mol−1)(×104 g·mol−1)
1 bAlCl32.473.8131.2717.904.973.61
2 cAlCl3/TiCl491.7163.1017.901.2414.41.24
3 bAlCl33.352.593.3825.476.703.81
4 cAlCl3/TiCl491.1162.0318.471.0018.61.74
5 bAlCl34.040.572.0428.867.593.81
6 cAlCl3/TiCl495.0168.9720.030.9620.92.35
7 bAlCl34.636.464.7427.235.794.71
8 cAlCl3/TiCl457.6102.4521.225.184.11.58
9 bAlCl35.115.427.3930.3011.222.71
10 cAlCl3/TiCl424.142.8731.5813.732.31.56
a 100 mL C2H2Cl2; Tp = −60 °C; tp = 30 min; b [AlCl3] = 2.51 mmol·L−1, [AlCl3]/[phenetole] = 1/1; c [AlCl3] = 1.26 mmol·L−1, [AlCl3]/[TiCl4]/[phenetole]/[H2O] = 1/1/1/1; d activity, kg PIB·mol−1(AlCl3 + TiCl4)·h−1; e Δ = activity(complexed catalyst)/activity(reference catalyst), where both the catalysts reacted at the same [IB].
Table
Table 4. Effect of polymerization time on the polymerization results a.
Table 4. Effect of polymerization time on the polymerization results a.
NoCoinitiatortpConv.Act. dMwMnMWDΔ e
(min)(%)(×104 g·mol−1)(×104 g·mol−1)
1AlCl3 b1.068.82200.2927.216.804.01.00
2AlCl3/TiCl4 c51.42744.0633.527.624.41.25
3AlCl3 b3.077.71242.4621.214.424.81.00
4AlCl3/TiCl4 c63.71700.3634.4313.242.61.37
5AlCl3 b5.092.3590.3711.970.4427.21.00
6AlCl3/TiCl4 c93.2995.1222.793.177.21.69
7AlCl3 b10.095.8306.3811.030.5320.81.00
8AlCl3/TiCl4 c90.1481.0223.604.375.41.57
9AlCl3 b30.0100.0106.6712.200.2646.11.00
10AlCl3/TiCl4 c95.0168.9020.030.9620.91.58
a [IB] = 4 mol·L−1; 100 mL C2H2Cl2; Tp = −60 °C; b [AlCl3] = 4.19 mmol·L−1, [AlCl3]/[phenetole] = 1/1; c [AlCl3] = 1.26 mmol·L−1, [AlCl3]/[TiCl4]/[phenetole]/[H2O] = 1/1/1/1; d activity, kg PIB·mol−1(AlCl3 + TiCl4)·h−1; e Δ = activity(complexed catalyst)/activity(reference catalyst), where the same tp lasted for the both initiating systems.

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Jin, Y.; Chen, L.; Guo, X.; Xu, L.; Zhu, Z.; Liu, Z.; Cheng, R.; Liu, B. A Complexed Initiating System AlCl3·Phenetole/TiCl4·H2O with Dominant Synergistic Effect for Efficient Synthesis of High Molecular Weight Polyisobutylene. Polymers 2019, 11, 2121. https://doi.org/10.3390/polym11122121

AMA Style

Jin Y, Chen L, Guo X, Xu L, Zhu Z, Liu Z, Cheng R, Liu B. A Complexed Initiating System AlCl3·Phenetole/TiCl4·H2O with Dominant Synergistic Effect for Efficient Synthesis of High Molecular Weight Polyisobutylene. Polymers. 2019; 11(12):2121. https://doi.org/10.3390/polym11122121

Chicago/Turabian Style

Jin, Yulong, Liang Chen, Xing Guo, Linfeng Xu, Zhihua Zhu, Zhen Liu, Ruihua Cheng, and Boping Liu. 2019. "A Complexed Initiating System AlCl3·Phenetole/TiCl4·H2O with Dominant Synergistic Effect for Efficient Synthesis of High Molecular Weight Polyisobutylene" Polymers 11, no. 12: 2121. https://doi.org/10.3390/polym11122121

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