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Hydroxy-functional poly(propenyl ether)s are promising thermoresponsive materials; here we establish a controlled synthesis via living cationic polymerization of silyl-protected monomers. Among the silyl protecting groups examined, only tert-butyldiphenylsilyl (TBDPS) enabled living cationic polymerization. The living cationic polymerization of tert-butyldiphenylsiloxybutyl propenyl ether (TBDPSBPE) afforded a high-molecular-weight polymer (poly(TBDPSBPE)) with a narrow molecular weight distribution (Mn = 12,900; Mw/Mn = 1.22). Additionally, chain propagation continued in monomer addition experiments, and the molecular weight increased further with a narrow molecular weight distribution, confirming the success of living cationic polymerization. Poly(TBDPSBPE) was successfully desilylated to afford poly(HBPE) with a narrow molecular weight distribution. Poly(HBPE) exhibited a glass transition temperature (Tg) of 44 °C, 82 °C higher than that of the corresponding polymer without β-methyl groups, poly(HBVE). The enhanced thermal properties of poly(HBPE) were attributed to the steric hindrance of the β-methyl group, which fixes the position of the hydroxy group and allows stronger hydrogen bonding. To investigate the aqueous thermoresponse, a hydroxylated analog with a shorter side-chain spacer (poly(HPPE)) was synthesized, and poly(HPPE) exhibited lower critical solution temperature (LCST)-type phase separation in water with a cloud-point temperature (Tcp) of 6 °C, showing reversible transitions with thermal hysteresis.

Despite a significant number of investigations in the field of phosphazene chemistry, the formation mechanism of this class of cyclic compounds is still poorly studied. At the same time, a thorough understanding of this process is necessary, both for the direct production of phosphazene rings of a given size and for the controlled cyclization reaction when it is secondary and undesirable. We synthesized a series of short linear phosphazene oligomers with the general formula Cl[PCl2=N]n–PCl3+PCl6– and studied their tendency to form cyclic structures under the influence of elevated temperatures or in the presence of nitrogen-containing agents, such as hexamethyldisilazane (HMDS) or ammonium chloride. It was established that linear oligophosphazenes are inert when heated in the absence of the mentioned cyclization agents, and the formation of cyclic products occurs only when these agents are involved in the process. The ability to obtain the desired size phosphazene cycle from corresponding linear chains is shown for the first time. Known obstacles, such as side interaction with the PCl6– counterion and a tendency of longer chains to undergo crosslinking elongation instead of cyclization are still relevant, and ways to overcome them are being discussed.

Block copolymers containing polytetrahydrofuran segments were synthesized by umpolung or propagating end of the cationic living polymer and successive anionic polymerization of methacrylates (RMAs) or radical polymerization of RMAs, acrylonitrile (AN), and styrene (St). Living polytetrahydrofuran (poly-THF) was prepared by cationic polymerization of tetrahydrofuran (THF), whose propagation end was reduced by samarium(II) iodide (SmI 2 ). Anionic polymerizations of RMAs were conducted by addition of the monomers to the reduced poly-THF to obtain poly(THF- b -RMAs). On the other hand, the 2-bromoisobutyrate group, which can act as an initiator of radical polymerization, was introduced to the cationic propagating end of poly-THF by adding sodium 2-bromoisobutyrate. Block copolymers were synthesized by living radical polymerization of RMAs, St, or AN using the 2-bromoisobutyrate-capped poly-THF as a macroinitiator and copper(I) bromide (CuBr) as a catalyst.

Due to the need to develop smart materials for a variety of applications such as catalysts and drug delivery, the development of photoresponsive polymers is receiving increasing attention. In particular, the photoisomerization of spiropyran (SP), unlike many other photoresponsive compounds, has attracted attention because it dramatically changes not only the molecular structure but also the polarity of the molecule. However, in most cases where SP is used as a photoresponsive functional group, SP is introduced in the side chain of the polymer, and few cases have been reported in which SP is introduced at the end of the polymer chain. Therefore, we designed a new amphipathic poly(vinyl ether) with an SP moiety at the end of the polymer chain. First, an initiator having an SP moiety was synthesized and used for living cationic polymerization to synthesize a poly(vinyl ether) bearing an SP moiety at the end of the polymer chain. Furthermore, we investigated the photoresponsive properties of the obtained polymers, we found that self-assembly of the amphiphilic polymers could be controlled by photoirradiation.

Living cationic copolymerization of 2-isopropyl-2-oxazoline with 2- n -propyl-, 2- n -butyl-, and 2- n -nonyl-2-oxazoline results in gradient copolymers of defined composition, narrow molar mass distributions (PDI = 1.09–1.3), and defined overall degree of polymerization, set to n  = 25 for all polymers. The introduction of monomer units of stronger amphiphilic character results in a systematic decrease of the lower critical solution temperature (LCST). The LCST modulation can be controlled by the choice of the comonomer as well as the comonomer ratio and was tuned in the temperature range from 46 to 9 °C.

A series of amphiphilic poly(vinyl ether)-based macromonomers having an aromatic ring, such as phenyl, naphthyl, and anthryl group, at ω -terminus (MA-PMEEVE-Ph, MA-PMEEVE-Nap, and MA-PMEEVE-Ant) were synthesized by living cationic polymerization and reductive amination. The obtained amphiphilic macromonomers possess narrow molecular distributions ( M w / M n  = 1.14–1.41) and well-controlled degree of polymerization (DP n  ≈ 40). In addition, the functionality of the ω -terminus is equal to unity for all the macromonomers. Then, copolymerizations of the obtained macromonomers with styrene in polar solvents were performed to form nearly monodisperse polymer particles. In order to clarify the effect of the terminal hydrophobic group on particle formation behavior, we have investigated the relationships between the feed ratio of the macromonomers to styrene and particle diameter ( D n ) and distribution of the particle diameter. As a result, MA-PMEEVE-Ant afforded the smallest polymer particle of D n  = 70 nm. It was also found that the particle diameter can be controlled by tuning the hydrophobicity of the ω -terminus group.

Imidophosphoric organic esters containing phosphoryl groups are potential polydentate ligands and promising extractants of rare-earth elements. For their preparation, a monophosphazene salt [PCl3=N−PCl3]+[PCl6]− and short phosphazene oligomers of the general formula [Cl–(PCl2=N)n–PCl3]+[PCl6]−, where n = 4–7, were synthesized via living cationic polymerization of Cl3P=NSiMe3 and used as starting compounds. All phosphazenes were reacted with 2-ethylhexanol to obtain the corresponding esters of imidophosphoric acids (EIPAs). The formation of imidophosphoric acids occurs due to the phosphazene-phosphazane rearrangement of –P(OR)2=N– or –P(OH)(OR)=N– units, where R = 2-ethylhexyl. The prepared EIPAs were characterized by 1H, 31P NMR, and MALDI-TOF analyses and their extractive capacity towards lanthanide ions in aqueous solutions of nitric acid was examined. The EIPAs are mixtures of mono-, di-, and trifunctional compounds of the type HxA, where x = 1–3, which can form chelate complexes of lanthanide ions [Ln(A)z], where z = 3–6, depending on the chain length. The longer chain EIPAs are more suitable for collective rare-earth elements extraction. A comparison of the extraction properties of the EIPAs with the industrially used polyalkylphosphonitrilic acid (PAPNA) was drawn.

Polymer particles modified with carbohydrates on their surfaces are of significant interest, because their specific recognition abilities to biomolecules are valuable for developing promising materials in biomedical fields. Carbohydrate-decorated core-shell polymer particles are expected to be efficiently prepared by dispersion polymerization using a glycopolymer-based amphiphilic macromonomer as both a polymeric steric stabilizer and a monomer. To create glycopolymer-type macromonomers, we propose a new strategy combining living cationic polymerization of an alkynyl-functionalized vinyl ether (VE), and the click reaction for the preparation of glycopolymers having a polymerizable terminal group, and investigate their dispersion copolymerization with styrene for generating carbohydrate-decorated polymer particles. This study deals with (i) the synthesis of block copolymer-type amphiphilic macromonomers bearing a methacryloyl group at the α-terminus, and pendant alkynyl groups by living cationic polymerization of alkynyl-substituted VE (VEEP), (ii) the derivatization of maltose-carrying macromonomers by click chemistry of the pendant alkynyl groups of the precursor macromonomers with maltosyl azide without any protecting/deprotecting processes, and (iii) the preparation of maltose-decorated (Mal-decorated) polymer particles through the dispersion copolymerization of glycopolymer-type macromonomers with styrene in polar media. Moreover, this study concerns the specific interactions of the resultant polymer particles with the lectin concanavalin A (Con A).

A highly effective initiating system has been achieved for living cationic polymerization of vinyl ethers consisting of HCl alone without Lewis acid. This system is a facile metal-free living cationic polymerization using no HCl/Lewis acid but the already adopted complex HCl·Et 2 O. In this study, we investigated the effects of a monomer and ether structure on the polymerization behavior. The monomers are classified into three kinds of monomers: alkyl vinyl ether, vinyl ether with electron-donating groups in the pendant, and vinyl ether with bulky group next to the electron-donating substituent in the pendant. The HCl·Et 2 O systems were applicable for the polymerizations of all vinyl ethers used. However the structure around electron-donating groups in the pendant of monomer affected the polymerizations rate and induction period. The initiation reactions can be successfully achieved using ether effectively dissociating HCl, especially symmetrical ether.

Heteroarm star-shaped polymers containing independent stimuli-responsive moieties were synthesized by a one-pot arm-linking reaction based on base-assisting living cationic polymerization. Mixing two or more kinds of living polymers followed by the linking reaction with a divinyl compound successfully produced a heteroarm star-shaped polymer containing a number of arm chains with a narrow molecular weight distribution ( M w / M n =1.14–1.48) and high yield. For example, four kinds of linear poly(vinyl ether)s containing oxyethylene and alicyclic pendants were linked quantitatively to give a star polymer without any deactivation of the starting polymers. The heteroarm star-shaped polymers exhibited their unique stimuli-responsive behaviors in water or their film surfaces. Furthermore, linear living poly(2-methoxyethyl vinyl ether) and poly(2-phthalimidoethyl vinyl ether) were linked efficiently despite their different reactivities, producing a heteroarm star-shaped polymer with amino-containing and thermosensitive arms. The obtained star polymer exhibited unique aggregation behaviors in response to both pH and temperature in water. This report demonstrates that this one-pot arm-linking reaction is a facile and effective methodology for synthesis of heteroarm star polymers with various combinations of stimuli-responsive arm chains. Highly efficient synthesis of heteroarm star-shaped polymers containing independent stimuli-responsive moieties was demonstrated using a one-pot arm-linking method via base-assisting living cationic polymerization. The linking reaction of mixed two or more kinds of living polymers with a divinyl compound successfully yielded heteroarm star polymers with narrow molecular weight distributions. Furthermore, this methodology was expanded to polar functional monomers, producing a heteroarm star-shaped polymer with amino-containing and thermosensitive arms. The obtained heteroarm star-shaped polymers exhibited their unique stimuli-responsive behaviors in water or their film surfaces.