The repeating guest units of poly‐(R)‐ 2 were selectively encapsulated by the self‐assembled capsule poly‐ 1 possessing eight polymer side chains to form the supramolecular graft polymer (poly‐ 1 )n?poly‐(R)‐ 2 . The encapsulation of the guest units was confirmed by 1H NMR spectroscopy and the DOSY technique. The hydrodynamic radius of the graft polymer structure was greatly increased upon the complexation of poly‐ 1 . The supramolecular graft polymer (poly‐ 1 )n?poly‐(R)‐ 2 was stably formed in the 1:1 host–guest ratio, which increased the glass transition temperature by more than 10 °C compared to that of poly‐ 1 . AFM visualized that (poly‐ 1 )n?poly‐(R)‐ 2 formed the networked structure on mica. The (poly‐ 1 )n?poly‐(R)‐ 2 gelled in 1,1,2,2‐tetrachloroethane, which led to fabrication of distinct viscoelastic materials that demonstrated self‐healing behavior in a tensile test. 相似文献
The repeating guest units of poly-(R)- 2 were selectively encapsulated by the self-assembled capsule poly- 1 possessing eight polymer side chains to form the supramolecular graft polymer (poly- 1 )n⋅poly-(R)- 2 . The encapsulation of the guest units was confirmed by 1H NMR spectroscopy and the DOSY technique. The hydrodynamic radius of the graft polymer structure was greatly increased upon the complexation of poly- 1 . The supramolecular graft polymer (poly- 1 )n⋅poly-(R)- 2 was stably formed in the 1:1 host–guest ratio, which increased the glass transition temperature by more than 10 °C compared to that of poly- 1 . AFM visualized that (poly- 1 )n⋅poly-(R)- 2 formed the networked structure on mica. The (poly- 1 )n⋅poly-(R)- 2 gelled in 1,1,2,2-tetrachloroethane, which led to fabrication of distinct viscoelastic materials that demonstrated self-healing behavior in a tensile test. 相似文献
By introducing slight structural modifications to a D4‐symmetric coordination capsule, we succeeded in isolating the nearly enantiopure capsules (P)‐ and (M)‐ 2 a (BF4)4. Chiral guest, dibenzyl 4,4′‐diacetoxy‐6,6′‐dimethyl‐[1,1′‐biphenyl]‐2,2′‐dicarboxylate ( 3 ) was encapsulated within the dissymmetric cavity of 2 a (BF4)4, resulting in a high diastereoselectivity of >99 % de. The encapsulated guest was successfully removed from the complex without racemization through precipitation of the empty capsule. CD spectra confirmed that the chirality of the capsule was maintained in THF and 1,4‐dioxane for long periods, whereas a small amount of acetonitrile accelerated racemization of the empty capsule. The activation parameters of the racemization reaction were determined in dichloromethane and 1,2‐dichloroethane, resulting in positive enthalpic contributions and large negative entropic contributions, respectively. Accordingly, the racemization fits a first‐order kinetic model. Mechanically coupled Cu+‐2,2′‐bipyridine coordination centers were responsible for the high‐energy barrier of racemization and led to the unique chiral memory of the dissymmetric cavity, which was turned off by the addition of acetonitrile. 相似文献
Novel dual molecular‐ and ion‐recognition responsive poly(N‐isopropylacrylamide‐co‐benzo‐12‐crown‐4‐acrylamide) (PNB12C4) linear copolymers with benzo‐12‐crown‐4 (B12C4) as both guest and host units are prepared. The copolymers exhibit highly selective sensitivities toward γ‐cyclodextrin (γ‐CD) and Na+. The presence of γ‐CD induces the lower critical solution temperature (LCST) of PNB12C4 copolymer to shift to a higher value due to the formation of 1:1 γ‐CD/B12C4 host‐guest inclusion complexes, while Na+ causes a negative shift in LCST due to the formation of 2:1 “sandwich” B12C4/Na+ host‐guest complexes. Regardless of the complexation order, when γ‐CD and Na+ coexist with PNB12C4, competitive complexation actions of B12C4 as both guest and host units toward γ‐CD and Na+ finally form equilibrium 2:2:1 γ‐CD/B12C4/Na+ composite complexes, and the final LCST values of PNB12C4 copolymer reach almost the same level. The results provide valuable guidance for designing and applying PNB12C4‐based smart materials in various applications.
Four novel crystalline stereocomplexed polymers are formed by mixing isotactic (R)‐ and (S)‐polycarbonates in 1:1 mass ratio. They show the enhanced thermal stability and new crystalline behavior, significantly distinct from the component enantiomer. Two stereocomplexed CO2‐based polycarbonates from meso‐3,4‐epoxytetrahydrofuran and 4,4‐dimethyl‐3,5,8‐trioxabicyclo[5.1.0]octane have high melting temperatures of up to 300 °C, about 30 °C higher than the individual enantiomers. Isotactic (R)‐ or (S)‐poly(cyclopentene carbonate) and poly(cis‐2,3‐butene carbonate) are typical amorphous polymeric materials, however, upon mixing both enantiomers together, a strong interlocked interaction between polymer chains of opposite configuration occurs, affording the crystalline stereocomplexes with melting temperatures of about 200 °C and 180 °C, respectively. A DFT study suggests that the driving force forming the stereocomplex is the hydrogen‐bonding between carbonate units of the opposite enantiomers. 相似文献
((?)‐Menthyl (S)‐6′‐acrylyl‐2′‐methyloxy‐1,1′‐binaphthalene‐2‐carboxylate ( 3 ) was synthesized and anionically polymerized using n‐BuLi as an initiator in toluene. The monomer 3 was levorotatory and had an [α]D25 value of ?72.4, but its corresponding polymer poly‐ 3 was dextrorotatory and showed an [α]D25 value of +162.0. Poly‐ 3 was confirmed to exist in the form of one‐handed helical structure in solution by means of comparing the specific optical rotation and the CD spectra with that of 3 and the model compounds such as (?)‐menthyl (S)‐6′‐propionyl‐2′‐methyloxy‐1,1′‐binaphthalene‐2‐carboxylate 2b and (?)‐menthyl (S)‐6′‐heptanoyl‐2′‐methyloxy‐1,1′‐binaphthalene‐2‐carboxylate 2c . This conclusion was also confirmed by the fact that the g‐value of poly‐ 3 is about 11 times of that of monomer 3 . 相似文献
A conjugated poly(phenyl‐co‐dibenzocyclooctyne) Schiff‐base polymer, prepared through polycondensation of dibenzocyclooctyne bisamine (DIBO‐(NH2)2) with bis(hexadecyloxy)phenyldialdehyde, is reported. The resulting polymer, which has a high molecular weight (Mn>30 kDa, Mw>60 kDa), undergoes efficient strain‐promoted alkyne–azide cycloaddition reactions with a series of azides. This enables quantitative modification of each repeat unit within the polymer backbone and the rapid synthesis of a conjugated polymer library with widely different substituents but a consistent degree of polymerization (DP). Kinetic studies show a second‐order reaction rate constant that is consistent with monomeric dibenzocyclooctynes. Grafting with azide‐terminated polystyrene and polyethylene glycol monomethyl ether chains of varying molecular weight resulted in the efficient syntheses of a series of graft copolymers with a conjugated backbone and maximal graft density. 相似文献
The ring‐opening polymerization of (R,S)‐β‐butyrolactone (BL) in bulk was analyzed with respect to the polymer structure of the resulting poly[(R,S)‐3‐hydroxybutanoate)] [P(3HB)] by isolation of the pure form using preparative supercritical CO2 fluid chromatography. It was confirmed that the four‐membered BL was polymerized in bulk by lipase to yield the corresponding cyclic, hydroxy‐ and crotonate‐terminated P(3HB)s. The relative ratios of the three types of polymers depended on the lipase concentration as well as on the monomer conversion. It was also confirmed that both cyclic and linear P(3HB) polymer species were subject to hydrolysis, and inter‐ and intramolecular transesterification by lipase to produce two series of polymers having linear and cyclic structures with higher and lower molecular weight. The formation of the cyclic P(3HB) iss regarded as the characteristic feature of the lipase‐catalyzed polymerization of BL. 相似文献
Upon complexation with PdII ions, precisely designed strandlike ligands with two tris(3,5‐pyridine) units at both terminals were assembled, with the aid of a linear template molecule, into a discrete tubular complex with a length of 3.5 nm. The high stability and the well‐defined structure of the coordination nanotube were revealed by NMR spectroscopy, cold‐spray ionization MS, and single‐crystal X‐ray analysis. Guest lengths were discriminated by the tube: When the association of strandlike guest molecules, in which two biphenylene units are linked with an (OCH2CH2)n linker, were compared, the tube selectively recognized an appropriate guest whose length was comparable to that of the tube. Tetrathiafulvalene (TTF)‐terminated linear guests were directly oxidized to TTF2+ in the tube, but reduced stepwise via TTF+? outside the tube. 相似文献
Novel functional polymers utilizing specific host/guest interactions were designed by introducing α‐CD host molecules into poly(ε‐lysine) chains as side groups. An interesting phase separation was observed as a result of the inclusion complexation between the polymeric host and 3‐(trimethylsilyl)propionic acid as a model guest in aqueous media. This water‐soluble polymeric host would be useful for various applications, particularly drug delivery, due to its biodegradability, low toxicity, and unique functionality represented as a complexation‐induced phase separation. 相似文献
The polymerization of bis(4‐ethynylphenyl)methylsilane catalyzed by RhI(PPh3)3 afforded a regio‐ and stereoregular hyperbranched polymer, hb‐poly[(methylsilylene)bis(1,4‐phenylene‐trans‐vinylene)] (poly( 1 )), containing 95% trans‐vinylene moieties. The weight loss of this polymer at 900°C in N2 was 9%. Poly( 1 ) displayed an absorption due to π‐π* transition around 275 nm as a shoulder and a weak absorption around 330 nm due to π‐to‐σ charge transfer, which was hardly seen in the corresponding linear polymer. 相似文献
A block copolymer based on poly(N‐isopropyl acrylamide) (PNIPAAm) and a block with a statistical distribution of poly(2‐hydroxyethyl acrylate) (PHEA) and repeating unit with carrying β‐cyclodextrin was prepared via reversible addition–fragmentation chain transfer (RAFT) polymerization and click reaction. Addition of poly(2‐hydroxyethyl acrylate‐s‐adamantylmethyl acrylate) P(HEA17‐s‐AdMA7) above the LCST of the block copolymer led to capture of the micelle structure of 36 nm against disassembly. The drug‐ (albendazole) loaded supramolecular assembly, which was fixed via host–guest complexation between β‐cyclodextrin and adamantane, was then tested as a drug carrier. Cell viability studies using human ovarian carcinoma cell line (OVCAR‐3) cell lines show a higher toxicity of the shell cross‐linked micelle compared with the free block copolymer. 相似文献