Liquid Crystalline Poly(vinyl ether)s and Block Copoly(vinyl ether)s by Living Cationic Polymerization

Abstract

A series of liquid crystalline (LC) poly(vinyl ether)s 1 was prepared by living cationic polymerization of a mesogenic vinyl ether monomer, 4-butoxyphenyl 4-((6-vinylhexyl)oxy)benzoate (11), in the presence of the HI/I2 (1/1 mol/mol) initiating system. The number average molar mass of polymers 1 increased linearly with the initial monomer to initiator molar ratio (M n = 3000−15 000 g mol-1, DPn ≈ 5−50), according to the living character of the polymerization, and their molar mass distribution was rather narrow (M w/M n = 1.10−1.15). Furthermore, two sets of AB diblock copoly(vinyl ether)s 2 and 3 were prepared by sequential polymerization of vinyl ether 11 and isobutyl vinyl ether (12) and chiral (S)-2-methylbutyl vinyl ether (13) respectively, by using the same HI/I2 system. While the average degree of polymerization of the LC block was kept constant (DPn ≈ 10), the length of the non-LC block was varied (DPn ≈ 2−25), according to the chosen feed conditions. An X-ray investigation proved that polymers 1 gave rise to a sequence of ordered smectic (F or I), smectic C, and nematic mesophases with increasing temperature. Their transition temperatures and entropies followed slightly different molar mass dependences, but each of them reached a saturation value at M n ≈ 6000 g mol-1. The same basic mesophase polymorphism was also observed for the LC block copolymers 2 and 3, thus suggesting that the chemically different blocks were microphase separated within the solid and LC phases.

Synthesis of side‐chain liquid‐crystalline homopolymers and triblock copolymers with p‐methoxyazobenzene moieties and poly(ethylene glycol) as coil segments by atom transfer radical polymerization and their thermotropic phase behavior

“…From the data of Table 3, the crystalline phase‐transition temperatures decreased from 62 to 43 °C, the corresponding enthalpy changes decreased from 184.1 to 22.6 J/g for PMMAZO‐ b ‐PEG12000‐ b ‐PMMAZO, and the crystalline phase‐transition temperatures decreased from 63 to 32 °C; the corresponding enthalpy changes decreased from 174.7 to 14.0 J/g for PMMAZO‐ b ‐PEG6000‐ b ‐PMMAZO with increasing molecular weight of the LC block on second heating. The disorder interfaces between the PEG and LC blocks possibly increase with increasing molecular weight of the LC block 7, 11, 29–31. Therefore, the crystallizability of the PEG block in the copolymers becomes poor.…”

Liquid crystalline side chain-coil diblock copolymers by living free radical polymerization

“…1). A M -n = 7 000 and a M -w /M -n = 1.18 were determined by SEC for poly(4-acetoxystyrene) (4). As the calculated value for poly(4-acetoxystyrene) in this condition is 7 300, we conclude that the molar mass of the poly(4-acetoxystyrene) block may be accurately controlled by adjusting the mole ratio monomer/ BPO.…”

“…Benzoyl peroxide (BPO), 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO), 2-fluoro-1-methylpyridinium p-toluenesulfonate (FMPTS) and anhydrous 1,2-dichlorobenzene were purchased from Aldrich and used as received. 4-oxybenzoate]-6-hexyl (4-vinylbenzoate) (3) monomer was prepared according to the synthetic procedure described in ref. 12) Block copolymers 2 a -b were prepared according to the synthetic route illustrated in Scheme 1.…”

“…To provide an effective route to tunable liquid crystalline (LC) properties, a variety of different synthetic approaches have been investigated with varying success including the living anionic polymerization 1) , living cationic polymerization [2][3][4] , group transfer polymerization 5) (GTP), polymer analog reactions, the use of macroinitiators and a combination of these routes. GTP polymerization is limited as it usually leads to low molar mass products while living anionic polymerization can not be applied to most monomers that carry functional groups typically used in LC polymers.…”

Síntese de copolímeros em bloco com propriedades líquido cristalinas

“…Desde então, uma série de trabalhos que envolvem rotas para produção dos mesmos foram sendo apresentados [5][6][7][8][9][10][11][12] . Pesquisadores italianos da Università di Piza e da Università di Bologna foram os que mais contribuíram para o desenvolvimento dessa área de pesquisa.…”