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Poly(α-methylene ester)s are an attractive type of functional aliphatic polyesters that represent a platform for the fabrication of various biodegradable and biomedical polymers. Herein, we report the controlled ring-opening polymerization (ROP) of a seven-membered α-methylene lactone (3-methylene-1,5-dioxepan-2-one, MDXO) that was synthesized based on the Baylis-Hillman reaction. The chemoselective ROP of MDXO was catalyzed by diphenyl phosphate (DPP) at 60 °C or stannous octoate (Sn(Oct) 2 ) at 130 °C, generating α-methylene-containing polyester (PMDXO) with a linear structure and easily tunable molar mass. The ring-opening copolymerization of MDXO with ε-caprolactone or 1,5-dioxepan-2-one was also performed under the catalysis of DPP or Sn(Oct) 2 to afford copolymers with different compositions and sequence structures that are influenced by the kinds of monomers and catalysts. PMDXO is a slowly crystallizable polymer with a glass transition temperature of ca. -33 °C, and its melting temperature and enthalpy are significantly influenced by the thermal history. The thermal properties of the copolymers are dependent on their composition and sequence structure. Finally, the post-modification of PMDXO based on the thiol-Michael addition reaction was briefly explored using triethylamine as a catalyst. Given the optimized condition, PMDXO could be dually modified to afford biodegradable polyesters with different functionalities.

Broad-band near-infrared (NIR) phosphors are essential to assembling portable NIR light sources for applications in spectroscopy technology. However, developing inexpensive, efficient, and thermally stable broad-band NIR phosphors remains a significant challenge. In this work, a phosphate, KAlP 2 O 7 , with a wide band gap and suitable electronic environment for Cr 3+ equivalent substitution was selected as the host material. The synthesized KAlP 2 O 7 :Cr 3+ material exhibits a broad-band emission covering 650-1100 nm with a peak centered at 790 nm and a full width at half-maximum (fwhm) of 120 nm under 450 nm excitation. The internal quantum efficiency (IQE) was determined to be 78.9%, and the emission intensity at 423 K still maintains 77% of that at room temperature, implying the high efficiency and excellent thermal stability of this material. Finally, a NIR phosphor-converted light-emitting diode (pc-LED) device was fabricated by using the as-prepared material combined with a 450 nm blue LED chip, which presents a high NIR output power of 32.1 mW and excellent photoelectric conversion efficiency of 11.4% under a drive current of 100 mA. Thus, this work not only provides an inexpensive broad-band NIR material with high performance for applications in NIR pc-LEDs but also highlights some strategies to explore this class of materials.

Broadband near-infrared (NIR) emitting materials are in great demand as next-generation smart NIR light sources. In this work, a Cr 3+ -substituted phosphor capable of efficiently converting visible to NIR light is developed through the solid solution, Ga 2- x In x O 3 :Cr 3+ (0 ≤ x ≤ 0.5). The compounds were prepared using high-temperature solid-state synthesis, and the crystal and electronic structure, morphology, site preference, and photoluminescence properties are studied. The photoluminescence results demonstrate a high quantum yield (88%) and impressive absorption efficiency (50%) when x = 0.4. The NIR emission is tunable across a wide range (713-820 nm) depending on the value of x . Moreover, fabricating a prototype of a phosphor-converted NIR light-emitting diode (LED) device using 450 nm LED and the [(Ga 1.57 Cr 0.03 )In 0.4 ]O 3 phosphor showed an output power that reached 40.4 mW with a photoelectric conversion efficiency of 25% driven by a current of 60 mA, while the resulting device was able to identify damaged produce that was undetectable using visible light. These results demonstrate the outstanding potential of this phosphor for NIR LED imaging applications.

To improve absorption efficiency (AE) and subsequently improve external quantum efficiency (EQE) remains one of the significant challenges for Mn 4+ -doped red-emitting fluoride phosphors. In this study, we propose to use Mn 4+ as a part of matrix to enhance the AE of fluoride phosphors. Red-emission phosphors Cs 2 MnF 6 , Cs 2 MnF 6 :Sc 3+ , and Cs 2 MnF 6 :Si 4+ were synthesized successfully by a coprecipitation method. The Rietveld refinement of X-ray diffraction reveals that this red phosphor exhibits a cubic structure in Fm 3̅ m space group. Owing to Mn 4+ being a part of matrix, this kind of red phosphor possesses an extremely high AE, which can be promoted to 88%. The doping of Sc 3+ and Si 4+ ions into Cs 2 MnF 6 can effectively increase the luminescence intensity to 253 and 232%, respectively, relative to that of Cs 2 MnF 6 . The relative emission intensity of Cs 2 MnF 6 :5%Si 4+ red phosphor preserves about 115% when temperature rises to 175 °C. By employing Cs 2 MnF 6 :5%Si 4+ as a red-emitting component, high-performance LED-1 with Ra = 86.2, R9 = 82.1 and CCT = 3297 K, and LED-2 with an ultrawide color gamut (NTSC value of 122.3% and rec. 2020 value of 91.3%) are obtained. This work may provide a new idea to explore a new type of fluoride phosphor with high EQE for high-performance white-light-emitting diodes.

Transient increase of reactive oxygen species (ROS) is vital for some physiological processes, whereas the chronic and sustained high ROS level is usually implicated in the inflammatory diseases and cancers. Herein, we report the innovative redox-responsive theranostic micellar nanoparticles that are able to load anticancer drugs through coordination and hydrophobic interaction and to fluorescently monitor the intracellular redox status. The nanoparticles were formed by the amphiphilic block copolymers composed of a PEG segment and a selenide-containing hydrophobic polycarbonate block with a small fraction of coumarin-based chromophore. Under the alternative redox stimulation that might be encountered in the physiological process of some healthy cells, these nanoparticles underwent the reversible changes in size, morphology, and fluorescence intensity. With the assistance of small model compounds, we clarified the chemistry behind these changes, that is, the redox triggered reversible transformation between selenide and selenoxide. Upon the monotonic oxidation similar to the sustained high ROS level of cancer cells, the nanoparticles could be disrupted completely, which was accompanied by the drastic decrease in fluorescence. Cisplatin and paclitaxel were simultaneously coloaded in the nanoparticles with a moderate efficacy, and the coordination between selenide and platinum improved the stability of the drug-loaded nanoparticles against dilution. The naked nanoparticles are cytocompatible, whereas the dual drug-loaded nanoparticles exhibited a concentration dependent and synergistic cytotoxicity to triple-negative breast cancer (TNBC) cells. Of importance, the drug-loaded nanoparticles are much more toxic to TNBC cells than to normal cells due in part to ROS overproduction in the former cell lines.

A new generation of red phosphors of complex fluoride matrices activated with Mn 4+ has gained a broad interest in getting high color quality and low color temperature of solid-state white light-emitting diodes (WLEDs). However, besides their instability toward moisture, the extremely irregular and nonuniform morphologies of these phosphors have limited their practical industry applications. In the present study, a novel type of K 3 ScF 6 :Mn 4+ red phosphor with highly regular, uniform, and high color purity was obtained successfully through a facile coprecipitation route under mild conditions. The crystal structure was identified with aids of the powder X-ray diffraction, Rietveld refinement, and density functional theory calculations. The prototype crystallizes in the space group Fm3 m with a cubic structure, and the lattice parameters are fitted well to be a = b = c = 8.4859(8) Å and V = 611.074(2) Å 3 . The Mn 4+ ions occupy Sc 3+ sites and locate at the centers of the distorted ScF 6 octahedrons. A wide band gap of approximately 6.15 eV can provide sufficient space to accommodate impurity energy levels. Unlike most other Mn 4+ ion-activated fluoride phosphors, the as-prepared K 3 ScF 6 :Mn 4+ phosphors demonstrate highly uniform and regular morphologies with shapes transforming from cube to octahedron with increasing Mn 4+ ion concentration. Under blue light excitation, the as-prepared K 3 ScF 6 :Mn 4+ sample exhibits intense sharp-line red fluorescence (the strongest peak located at 631 nm) with high color purity. An excellent recovery in luminescence upon heating and cooling processes implies high stability of K 3 ScF 6 :Mn 4+ . Furthermore, a warm WLED fabricated with blue GaN chips merged with the mixture of K 3 ScF 6 :Mn 4+ and the well-known commercial YAG:Ce 3+ yellow phosphors exhibits wonderful color quality with lower correlated color temperature (3250 K) and higher color-rendering index ( R a = 86.4). These results suggest that the K 3 ScF 6 :Mn 4+ phosphor possesses stupendous potentiality for practical applications.

Reactive oxygen species (ROS)-responsive polymers have attracted attention for their potential in photodynamic therapy. Herein, we report the ROS-responsive aliphatic polycarbonates prepared by the ring-opening polymerization (ROP) of three six-membered cyclic carbonate monomers with ethyl selenide, phenyl selenide or ethyl telluride groups. Under catalysis of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), all three monomers underwent the controlled anionic ROP, showing a feature of equilibrium polymerization due to the bulky effect of 5,5-disubstituents. With PEG macroinitiator, three series amphiphilic block copolymers were prepared. They could form spherical nanoparticles of ∼100 nm, which were stable in neutral phosphate buffer but dissociated rapidly under triggering of H 2 O 2 . We studied the H 2 O 2 -induced oxidation profiles of selenide- or telluride-containing small molecules by 1 H NMR and revealed the factors that affect the oxidation kinetics and products. On this basis, the oxidative degradation mechanism of the copolymer nanoparticles has been clarified. Under the same oxidative condition, the telluride-containing nanoparticle degraded with the fastest rate while the phenyl selenide-based one degraded most slowly. These ROS-responsive nanoparticles could load photosensitizer chlorin e6 (Ce6) and anticancer drug doxorubicin (DOX). Under red light irradiation, Ce6-sensitized production of 1 O 2 that triggered the degradation of nanoparticles, resulting in an accelerated payload release. In vitro cytotoxicity assays demonstrate that the nanoparticles coloaded with DOX and Ce6 exhibited a synergistic cell-killing effect to MCF-7 cells, representing a novel responsive nanoplatform for PDT and/or chemotherapy.

Reactive oxygen species (ROS)-responsive theranostic nanomedicines have attracted wide interest in recent years because ROS stress is implicated in some pathological disorders such as inflammatory diseases and cancers. In this article, we report a kind of innovative ROS-responsive theranostic polymeric nanoparticles that are able to load hydrophobic drugs and to fluorescently self-report the in vitro or intracellular drug release under ROS triggering. The fluorescent nanoparticles were formed by amphiphilic block copolymers consisting of a poly(ethylene glycol) (PEG) segment and an oxidation-responsive hydrophobic block. The copolymers with different hydrophobic block lengths were synthesized by the atom transfer radical polymerization of a phenylboronic ester-containing acrylic monomer with a small fraction of a ROS-activatable 1,8-naphthalimide-based fluorescent monomer, using PEG-Br as the macroinitiator. The copolymer nanoparticles were stable in neutral phosphate buffer but degraded upon H 2 O 2 triggering, with the degradation rate depending on the hydrophobic block length and the concentration of H 2 O 2 . The degradation of nanoparticles was accompanied by a colorimetric change of the fluorophore from blue to green, which affords the nanoparticles the ability to detecting H 2 O 2 by a ratiometric fluorescent approach. Moreover, the nanoparticles could encapsulate doxorubicin (DOX) and the H 2 O 2 -triggered DOX release was well associated with the change in ratiometric fluorescence. Confocal laser scanning microscope results reveal that the fluorescent nanoparticles were internalized into A549 cells through the endocytosis pathway. The ROS-stimulated degradation of the nanoparticles and intracellular DOX release and the fate of the degraded polymers could be monitored by ratiometric fluorescent imaging. Finally, the naked nanoparticles and the degradation products are cytocompatible, whereas the DOX-loaded ones exhibit concentration-dependent cytotoxicity. Of importance, the stimulation with exogenous H 2 O 2 or lipopolysaccharide enhanced obviously the cell-killing capability of the DOX-loaded nanoparticles because of the ROS-enhanced intracellular DOX release.

The selective Passerini reactions of 4-formylbenzoic acid and 4-isocyanobenzoic acid with aliphatic isocyanides and aldehydes were utilized to synthesize sequence-defined uniform macromolecules. Our strategy does not involve any protecting groups or reactive group transformation steps and allows direct and consecutive propagation of sequence in each step. Introduction of diverse side groups by using different aliphatic components provided a range of sequence-defined uniform macromolecules in high yield and gram scale. The strategy also allows further Passerini self-coupling or cross-coupling of the formed sequences with other small molecules, affording polymers with up to 5098.3 Da and 20 side groups. Thus, this strategy will show promise for more efficient synthesis of new sequence-defined macromolecules.

Lu 3+ , with the smallest ionic radii in lanthanide ions, is an important and beneficial cation for tuning spectrum shifting toward a longer wavelength by ion substitution in many phosphors for solid-state lighting. However, in the Lu 3+ -substituted garnet system, the phosphor always has smaller lattice parameters and exhibits a shorter emission wavelength than other garnet phosphors. The mechanism of such a spectral blue shift induced by the Lu 3+ -codoped garnet phosphor is still unclear. In this study, the local and electronic structures of Lu 3+ -codoped and Lu 3+ -undoped YAG:Ce 3+ phosphor have been studied by first-principles calculation to reveal the origin of the spectral blue shift. Our results provide a full explanation of the experimental data and the methodology, which is useful to understand and design garnet phosphors with tunable emission characteristics., Competing Interests: The authors declare no competing financial interest.

Reactive oxygen species (ROS)-responsive polymers and hydrogels represent an emerging family of intelligent materials owing to the key functions of ROS in physiological processes or pathological diseases. Nonetheless, the weaknesses such as low sensitivity, slow response, instability, and low mechanical strength are associated with the limited ROS-responsive polymeric or supramolecular hydrogels. In this study, a novel type of oxidation-responsive degradable hydrogels was fabricated by the redox-initiated radical polymerization of a 4-arm-poly(ethylene glycol) (PEG) acrylic macromonomer that possesses a H 2 O 2 -cleavable phenylboronic acid linker in each of the arms. The macroscopic hydrogels have the features of good cytocompatibility, moderate mechanical strength, and fast response toward H 2 O 2 of low concentration, owing to the covalently cross-linked hydrophilic PEG network and high sensitivity of the linker. They could encapsulate biomacromolecules, such as insulin and glucose oxidase (GOx), with high efficacy, affording a new glucose-responsive insulin-delivery platform on the basis of enzymatic transformation of a biochemical signal (glucose) into an oxidative stimulus (H 2 O 2 ). Interestingly, in vitro results demonstrate that the same GOx-loaded hydrogel exhibited disparate degradation modes under different triggering molecules, that is, bulk degradation by H 2 O 2 and surface erosion by glucose. Moreover, compared to the macroscopic hydrogel, the nanogel with a diameter of ∼160 nm prepared by inverse emulsion polymerization showed a much higher degradation rate even under triggering of 20 μM H 2 O 2 , a pathologically available concentration in vivo.

We report the straightforward synthesis of two types of H 2 O 2 -cleavable poly(ester-amide)s ( P1 and P2 ) via the Passerini multicomponent polymerization (P-MCP) of 4-formylbenzeneboronic acid pinacol ester with 1,6-diisocyanohexane and 1,6-hexanedioic acid or a polyethylene glycol (PEG) dicarboxylic acid. The H 2 O 2 -cleavable phenylboronic acid ester was integrated into the polymer backbone by the in situ formed benzyl ester bond. GPC and 1 H NMR confirmed the complete H 2 O 2 -triggered degradation of these polymers in aqueous medium by a mechanism of sequential oxidation of phenylboronic acid ester and self-immolative elimination. Compared with the hydrophobic polymer P1 , the PEG-based water-soluble polymer P2 degraded much faster even at a lower H 2 O 2 concentration. Cytocompatible nanoparticles of polymer P1 loaded with fluorescent Nile red were fabricated, and controlled release of Nile red in response to H 2 O 2 was achieved, thus, demonstrating the utility of these polymers as potential H 2 O 2 -responsive delivery vehicles.

We report a new type of oxidation-promoted fast-degradable aliphatic poly(carbonate)s (PCs) prepared by the ring-opening polymerization (ROP) of a six-membered cyclic carbonate containing a phenylboronic pinacol ester. The ROP of this monomer catalyzed by 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) proceeded rapidly at ambient temperature with a good control over molecular weight and polydispersity at high monomer conversion. The H 2 O 2 -induced decomposition of this cyclic monomer and its noncyclic carbonate analogue was first studied by 1 H NMR in order to clearly demonstrate the degradation mechanism of the PCs. The results of 1 H NMR, GPC, and Nile Red fluorescence measurements revealed that the PC nanoparticles formulated by the o/w emulsion method were stable in neutral buffer, but upon triggering with H 2 O 2 , they underwent rapid surface degradation via the consecutive processes of oxidation, 1,6-elimination, release of CO 2 , and intramolecular cyclization. The degradation rates of the nanoparticles were dependent on the concentration of H 2 O 2 , and the nanoparticles were even sensitive to 0.5 mM of H 2 O 2 .

We demonstrate a new type of acid-sensitive amphiphilic polypseudorotaxanes (PPRs) formed via inclusion complexation between Pluronic F127 and the hydrophobic β-cyclodextrin (CD) derivative in alcoholic solvents. The 6-OH ortho ester-substituted hydrophobic β-CD derivative (EMD-CD) was prepared by "click" reaction of β-CD with 2-ethylidene-4-methyl-1,3-dioxalane under mild conditions. The water-insoluble EMD-CD (host) is capable of forming PPRs with F127 (guest) in ethanol or methanol but not in water, which is confirmed by 1 H NMR, wide-angle X-ray diffraction, small-angle X-ray scattering, and the time-dependent threading kinetics. Depending on the host/guest ratio, the PPRs self-assembled into sheet-like structure or vesicular nanoparticles with different sizes in water. These PPR assemblies were stable at pH 8.4 but quickly dissociated into biocompatible products in neutral or in acidic buffers due to the hydrolysis of the ortho ester groups. Good biocompatibility, ease of fabrication, and extremely pH-sensitive character make the PPRs promising carriers for anticancer drug delivery. Moreover, the present work provides an alternative method for the preparation of PPRs composed of water-insoluble CD derivatives.

We report a new type of pH-sensitive supramolecular aggregates which possess a programmable character of sequential dePEGylation and degradation. As a platform of designing and building multifunctional supramolecular nanoparticles, a family of 6-OH ortho ester-modified β-cyclodextrin (β-CD) derivatives have been synthesized via the facile reaction between β-CD and cyclic ketene acetals with different alkyl lengths. These asymmetric acid-labile β-CD derivatives formed amphiphilic supramolecules with adamantane-modified PEG through host-guest interaction in polar solvents such as ethanol. The supramolecules can self-assemble in water to form acid-labile supramolecular aggregates. The results of TEM and light scattering measurements demonstrate that the size and morphology of the aggregates are influenced by the alkyl or PEG length and the host-guest feed ratio. By carefully balancing the alkyl and PEG lengths and adjusting the host-guest ratio, well-dispersed vesicles (50-100 nm) or sphere-like nanoparticles (200-500 nm) were obtained. Zeta potential measurements reveal that these supramolecular aggregates are capable of being surface-functionalized via dynamic host-guest interaction. The supramolecular aggregates were stable at pH 8.4 for at least 12 h as proven by the (1)H NMR and LLS measurements. However, rapid dePEGylation occurred at pH 7.4 due to the hydrolysis of the ortho ester linkages locating at the interface, which resulted in aggregation of the dePEGylated hydrophobic inner cores. Upon further decreasing the pH to 6.4, the hydrophobic cores were further degraded due to the acid-accelerated hydrolysis of the ortho esters. The incubation stability of the acid-labile supramolecular aggregates in neutral buffer could be improved by incorporating hydrophobic poly(ε-caprolactone) into the core of the aggregates.

Synthesis of dendrimers has been directed toward process efficiency and structural diversity. We report a divergent approach to the preparation of dendrimers with both ABC and ABB branching structures from nonbranching monomers by combination of efficient orthogonal ABC Passerini multicomponent reaction (MCR) and ABB thiol-yne MCR. Two kinds of dendrimers were synthesized efficiently: (1) dendrimers with two generations in three steps and (2) dendrimers with two generations containing one kind of internal functional group and two kinds of surface functional groups in five steps. This new synthetic method offers an efficient access to dendrimers with structural diversity.

A series of well-defined thermoresponsive diblock copolymers (PEO45-b-PtNEAn, n=22, 44, 63, 91, 172) were prepared by the atom transfer radical polymerization of trans-N-(2-ethoxy-1,3-dioxan-5-yl) acrylamide (tNEA) using a poly(ethylene oxide) (PEO45) macroinitiator. All copolymers are water-soluble at low temperature, but upon quickly heating to 37 °C, laser light scattering (LLS) and transmission electron microscopy (TEM) characterizations indicate that these copolymers self-assemble into aggregates with different morphologies depending on the chain length of PtNEA and the polymer concentration; the morphologies gradually evolved from spherical solid nanoparticles to a polymersome as the degree of polymerization ("n") of PtNEA block increased from 22 to 172, with the formation of clusters with rod-like structure at the intermediate PtNEA length. Both the spherical nanoparticle and the polymersome are stable at physiological pH but susceptible to the mildly acidic medium. Acid-triggered hydrolysis behaviors of the aggregates were investigated by LLS, Nile red fluorescence, TEM, and (1)H NMR spectroscopy. The results revealed that the spherical nanoparticles formed from PEO45-b-PtNEA44 dissociated faster than the polymersomes of PEO45-b-PtNEA172, and both aggregates showed an enhanced hydrolysis under acidic conditions. Both the spherical nanoparticle and polymersome are able to efficiently load the hydrophobic doxorubicin (DOX), and water-soluble fluorescein isothiocyanate-lysozyme (FITC-Lys) can be conveniently encapsulated into the polymersome without using any organic solvent. Moreover, FITC-Lys and DOX could be coloaded in the polymersome. The drugs loaded either in the polymersome or in the spherical nanoparticle could be released by acid triggering. Finally, the DOX-loaded assemblies display concentration-dependent cytotoxicity to HepG2 cells, while the copolymers themselves are nontoxic.

We report a versatile method to tune the hydrolysis of the ortho ester-containing block copolymers by covalently incorporating oxidation-sensitive phenylboronic ester units. A series of block copolymers which contain a polyethylene glycol (PEG) block and a hydrophobic segment composed of different amounts of pendent ortho ester and phenylboronic ester groups were synthesized. These copolymers can self-assemble into narrowly dispersed micelle-like nanoparticles in phosphate buffer. The kinetics of phenylboronic ester oxidation and ortho ester hydrolysis in the nanoparticles were studied at different pH and H 2 O 2 concentration. The results indicated that the phenylboronic ester oxidation rate was faster than the ortho ester hydrolysis rate at neutral pH, and both processes were accelerated with increasing H 2 O 2 concentration. Nanoparticles which are extremely sensitive to the biorelevant concentration of H 2 O 2 (50 μM) at pH 7.4 were obtained, suggesting great promise for inflammation-specific drug delivery.

Multicomponent polymerization based on Passerini reaction is described. Room temperature polymerization of dicarboxyl acid, monoaldehyde, and diisocyanide leads to the formation of a new type of sequence regulated poly(ester-amide)s in an efficient one-pot process. The polymerization was confirmed to be a stepwise mechanism, and the resulting polymers were characterized and determined to be linear polymers with a sequence regulated backbone repeating unit of ester-ester-amide-amide. When functional aldehydes were used, functional side groups could be easily introduced at the same time, providing a simple way for further modification.

This work presents a facile approach for preparation of acid-labile and biocompatible polymers with pendent cyclic ortho esters, which is based on the efficient and mild reactions between cyclic ketene acetal (CKA) and hydroxyl groups. Three CKAs, 2-ethylidene-1,3-dioxane (EDO), 2-ethylidene-1,3-dioxolane (EDL), and 2-ethylidene-4- methyl-1,3-dioxolane (EMD) were prepared from the corresponding cyclic vinyl acetals by catalytic isomerization of the double bond. The reaction of CKAs with different alcohols and diols was examined using trace of p-toluenesulfonic acid as a catalyst. For the monohydroxyl alcohols, cyclic ortho esters were formed by simple addition of the hydroxyl group toward CKAs with ethanol showing a much greater reactivity than iso-propanol. When 1,2- or 1,3-diols were used to react with the CKAs, we observed the isomerized cyclic ortho esters besides the simple addition products. Biocompatible polyols, that is, poly(2-hydroxyethyl acrylate) (PHEA) and poly(vinyl alcohol) (PVA) were then modified with CKAs, and the degree of substitution of the pendent ortho esters can be easily tuned by changing feed ratio. Both the small molecule ortho esters and the CKA-modified polymers demonstrate the pH-dependent hydrolysis profiles, which depend also on the chemical structure of the ortho esters as well as the polymer hydrophobicity.

Linear reduction-degradable cationic polymers with different secondary amine densities (S2 and S3) and their nonreducible counterparts (C2 and C3) were synthesized by Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) step-growth polymerization of the dialkyne-oligoamine monomers and the diazide monomers. These polymers were studied with a goal of developing a set of new gene carriers. The buffering capacity and DNA binding ability of these polymers were evaluated by acid-base titration, gel retardation, and ethidium bromide (EB) exclusion assay. The polymers with lower amine density exhibit a weaker DNA-binding ability but a stronger buffering capacity in the range of pH 5.1 and 7.4. Particle size and zeta-potential measurements demonstrate that the polymers with higher amine density condense pDNA to form polyplexes with smaller sizes, while the disulfide bond in the backbone shows a negative effect on the condensing capability of the polymers, resulting in the formation of polyplexes with large size and nearly neutral surface. The reduction-sensitive polyplexes formed by polymer S2 or S3 can be disrupted by dithiothreitol (DTT) to release free DNA, which has been proven by the combination of gel retardation, EB exclusion assay, particles sizing, and zeta potential measurements. Cell viability measurements by MTT assay demonstrate that the reduction-degradable polymers (S2 and S3) have little cytotoxicity while the nonreducible polymers (C2 and C3) show obvious cytotoxicity, in particular, at high N/P ratios. In vitro transfection efficiencies of these polymers were evaluated using EGFP and luciferase plasmids as the reporter genes. Polymers S3 and S2 show much higher efficiencies than the nonreducible polymers C3 and C2 in the absence of 10% serum; unexpectedly, the lowest transfection efficiency has been observed for polymer S3 in the presence of serum.

A((=))-D, [A((=))](2)-D and [A ((=))](3)-D multi-maleimides and multi-itaconimides bearing electron-donating chromophores display a strong fluorescence quenching due to an intramolecular charge-transfer interaction. The electron-accepting C=C bond plays a key role in the intramolecular quenching. For the isomerization of these multi-itaconimides and Michael additions of these multi-maleimides, their emission behavior is irreversible. For the Diels-Alder additions of these multi-maleimides, their emission behavior is reversible due to the reversible opening and closing of intramolecular charge-transfer pathway. Tris-maleimide TMPA peripherally modified with furfural alcohol displays not only reversible fluorescence behavior but also reversible aggregation behavior.

A convenient synthetic route to prepare amine-terminated poly(ethylene oxide) (PEO) and poly(epsilon-caprolactone) (PCL) was described. The strategy involved two-step reactions, the condensation of hydroxyl-terminated PEO and PCL with N-benzyloxycarbonyl amino acid followed by the catalytic hydrogenation under mild conditions. NMR and GPC measurements indicated that the reactions proceeded nearly quantitatively. Amine-terminated PEO thus prepared was used to initiate the polymerization of alpha-(N(epsilon)-benzyloxycarbonyl-L-lysine) N-carboxy anhydride [lys(Z)-NCA], and the results confirmed that the reactivity of the amino group was high.