Aspects of the Synthesis of Poly(styrene-block-isobutylene-block-styrene) by TiCl4-Co-initiated Cationic Polymerization in Open Conditions

Abstract

The cationic polymerization of isobutylene and its block copolymerization with styrene using DiCumCl/TiCl4/2,6-lutidine initiating system has been studied in open conditions. It was shown that a higher concentration of proton trap is required in open conditions as compared to the glove box technique in order to have good control over molecular weight and polydispersity. Polyisobutylenes with Mn ≤ 50,000 g mol−1 and low polydispersity (Đ ≤ 1.2) were prepared at [Lu] = 12 mM. The synthesis of poly(styrene-block-isobutylene-block-styrene) triblock copolymer (SIBS) in open conditions required the addition of proton trap into two steps, half at the beginning of the reaction and the second half together with styrene. Following this protocol, a series of triblock copolymers with different length of central polyisobutylene block (from Mn = 20,000 g mol−1 to 50,000 g mol−1) and side polystyrene blocks (Mn = 4000 g mol−1–9000 g mol−1) with low polydispersity (Đ ≤ 1.25) were synthesized. High molecular SIBS (Mn > 50,000 g mol−1) with low polydispersity (Đ < 1.3) containing longer polystyrene blocks (Mn > 6000 g mol−1) demonstrated higher tensile strength (~13.5 MPa).

Biomaterials Based on Carbon Nanotube Nanocomposites of Poly(styrene-b-isobutylene-b-styrene): The Effect of Nanotube Content on the Mechanical Properties, Biocompatibility and Hemocompatibility

“…Initially, SIBS-2 with high molecular weight was six times stronger than SIBS-1, showed higher percentage of ultimate strain (28%, p < 0.01) and did not differ in Young’s modulus ( p = 0.99) ( Figure 6 e–g). This difference in tensile strength is consistent with the higher length of polystyrene side blocks in SIBS-2 (M n ~15,000 g mol −1 ) as compared to SIBS-1 (M n ~8700 g mol −1 ) [ 30 , 43 ]. Since SIBS belongs to the thermoplastic elastomer family, the increase in the length of “hard” polystyrene block results in the enhancement of interaction between polystyrene blocks of different polymer chains in polystyrene domains that, in turn, leads to the increase of tensile strength.…”

“…In this study, two samples of SIBS were prepared by the sequential cationic polymerization of isobutylene and styrene with dicumyl chloride/TiCl 4 /2,6-lutidine initiating system following the protocol mentioned in our previous study [ 30 ]. Two triblock copolymer samples with similar content of styrene in the copolymer but different number-average molecular weight and, therefore, different length of both of blocks were prepared ( Table 1 , Figures S1 and S2 ).…”

“…Two triblock copolymer samples with similar content of styrene in the copolymer but different number-average molecular weight and, therefore, different length of both of blocks were prepared ( Table 1 , Figures S1 and S2 ). Low molecular weight SIBS (SIBS-1) is characterized by a monomodal molecular weight distribution, while the high molecular weight copolymer (SIBS-2) showed small shoulder in high molecular weight region due to the intermolecular alkylation [ 30 ]. The complete shift of SEC traces into high molecular weight region upon addition of styrene to living polyisobutylene chains confirms the successful formation of triblock copolymers in both cases ( Figure S1 ).…”

Quasiliving carbocationic polymerization of isobutylene using FeCl3 as an efficient and water-tolerant Lewis acid: synthesis of well-defined telechelic polyisobutylenes

“…In addition, due to the high sensitivity of TiCl 4 to H 2 O, perfectly anhydrous conditions and invariable addition of a proton trap are required to suppress the undesirable initiation by protic impurities. 1,28,[34][35][36][37][38][39][40]44 Recently, Wu and co-workers reported a new FeCl 3 -based initiating system for the living cationic polymerization of isobutylene. It was particularly shown that the dicumyl chloride (DiCumCl)/FeCl 3 / i PrOH initiating system afforded difunctional polyisobutylenes with a controlled molecular weight (M n up to 25 000 g mol −1 ) as well as triblock copolymers of isobutylene with styrene.…”

“…In addition, due to the high sensitivity of TiCl 4 to H 2 O, perfectly anhydrous conditions and invariable addition of a proton trap are required to suppress the undesirable initiation by protic impurities. 1,28,34–40,44…”