A New Synthesis Strategy on Styrene-Butadiene Di-Block Copolymer Containing High cis-1,4 Unit Via Transfer of Anionic to Coordination Polymerization

Effects of Structurally Different Tertiary Amines on the Properties of Quaternized Anionic Exchange Membranes Potentially Applicable for Water Electrolysis

In this work, two structurally different monoamines (trimethylamine [TMA] and N-methylpiperidine [N-MPip]) are used for the amination of a g-VBC-15 graft copolymer, obtained by the functionalization of a mechanically robust, commercially available styrene-butadiene block copolymer (SB) with vinylbenzyl chloride (VBC) via solution free-radical polymerization. Results demonstrate that g-VBC-15-based membranes quaternized with TMA have superior electrochemical performance than N-MPip counterparts; while, the mechanical properties are good and only slightly inferior to those of N-MPip. Therefore, TMA is the selected monoamine to be alternatively mixed with two polyamines (tetramethyl-1,3-propanediamine [TMPDA] and N,N,N',N'',N''-pentamethyldiethylenetriamine [PMDETA]) into different proportions, in order to modulate the average functionality of the amination mixture in terms of number of amine functional groups available for the quaternization reaction of the membranes. g-VBC-15-based membranes derived therefrom are extensively characterized to assess their thermal, mechanical, and ex situ electrochemical properties. Results indicate that membranes quaternized with a TMA/PMDETA mixture (90:10 in mole) display the highest conductivity among all the investigated membranes aminated with polyamine-based mixtures. Moreover, they have comparable mechanical and electrochemical properties to those quaternized with TMA, while exhibiting a reduced water uptake.

Synthesis of block copolymer with cis-1,4-polybutadiene and isotactic-rich polystyrene using α-diimine nickel catalysts

A series of styrene-butadiene di-block copolymers with high cis-1,4 unit content (greater than 92%) polybutadiene (PB) and isotactic-rich polystyrene (PS) (mmmm > 65%) was synthesized using α-diimine nickel catalysts (Ni-diimine). Four different Ni-diimine catalysts were synthesized via a complexing reaction between nickel (II) naphthenate and laboratory-made α-diimine ligands L1, L2, L3 and L4, which have different steric volume structures. The results indicate that the Ni-diimine catalyst prepared using the L4 ligand with a higher steric volume can effectively initiate the block polymerization of butadiene and styrene, and the resulting polymer has distinguished cis-1,4 structure unit PB and high isotactic-selective PS block. Differential scanning calorimetry and electrochemical performance tests show that these block copolymers with cis-1,4-regulated and isotactic-selective polymerization have advantages in terms of high-temperature and low-temperature resistance as well as corrosion resistance. Therefore, these copolymers are expected to be widely used in some harsh industrial environments.

Scandium-catalyzed stereoselective block and alternating copolymerization of diphenylphosphinostyrenes and isoprene

The coordination copolymerization of polar diphenylphosphinostyrenes (StPPh2) and isoprene (IP) by a half-sandwich scandium catalyst (C5Me4SiMe3)Sc(CH2C6H4NMe2-o)2 afforded a new series of phosphine-functionalized alternating and block isoprene-styrene copolymers. In the copolymerization...

A New Strategy for the Synthesis of Hydroxyl Terminated Polystyrene-b-Polybutadiene-b-Polystyrene Triblock Copolymer with High Cis-1, 4 Content

This work reports the preparation of a hydroxyl terminated polystyrene-b-polybutadiene-b-polystyrene triblock copolymer (SBS) with high cis-1, 4 content via a novel nickel catalyst, [η³-Ni(CH₂CHCHCH₂OOCH₃)][BPh^F₄]. FT-IR, ¹H-NMR, and ¹³C NMR indicated that the polybutadiene segment of the copolymer contains greater than 90% cis-1, 4 structure, indicating achievement of the objective. Toward the functionalization goal, a hydroxyl group was successfully introduced at the end of the triblock copolymer (HO–SBS–OH). The results of gel permeation chromatography (GPC) revealed that the polymer is indeed a triblock copolymer, with no traces of homopolymer. Differential scanning calorimetry (DSC) showed that HO–SBS–OH synthesized using the novel catalyst had a lower glass transition temperature (T_g) than HO–SBS–OH synthesized with an alkyl lithium catalyst. Therefore, the polymer synthesized via the novel catalyst contains high cis-1,4 content and displays excellent low-temperature mechanical properties.