Carbon‐Nanotube‐Mediated Electrochemical Transition in a Redox‐Active Supramolecular Hydrogel Derived from Viologen and an l‐Alanine‐Based Amphiphile

A two‐component hydrogelator (16‐A)₂‐V²⁺ , comprising an l ‐alanine‐based amphiphile ( 16‐A ) and a redox‐active viologen based partner ( V²⁺ ), is reported. The formation the hydrogel depended, not only on the acid‐to‐amine stoichiometric ratio, but on the choice of the l ‐amino acid group and also on the hydrocarbon chain length of the amphiphilic component. The redox responsive property and the electrochemical behavior of this two‐component system were further examined by step‐wise chemical and electrochemical reduction of the viologen nucleus (V²⁺/V⁺ and V⁺/V⁰). The half‐wave reduction potentials (E_1/2) associated with the viologen ring shifted to more negative values with increasing amine component. This indicates that higher extent of salt formation hinders reduction of the viologen moiety. Interestingly, the incorporation of single‐walled carbon nanotubes in the electrochemically irreversible hydrogel (16‐A)₂‐V²⁺ transformed it into a quasi‐reversible electrochemical system.     

Conductance Switch of a Bromoplumbate Bistable Semiconductor by Electron‐Transfer Thermochromism

Electron‐transfer (redox) thermochromism was successfully used for switching the conductance of semiconductors, by introducing a thermally active organic component into an inorganic semiconducting framework. A moisture‐resistant semiconductor {(MV)₂[Pb₇Br₁₈]}_n (MV²⁺=methyl viologen cation) has been prepared through an in situ synthetic method for MV²⁺. It features a rare 3D haloplumbate open framework and unprecedented electron‐transfer thermochromic behavior in haloplumbates. The electrical conductivity of this compound dropped significantly after coloration and restored after decoloration, which was satisfactorily explained by valence band XPS and theoretical data. This work not only offers a new approach to modify electrical properties of semiconductors without altering components or structures, but may lead to the development of over‐temperature color indicators, circuit overload protectors or photovoltaic materials.     

para‐Phenylene‐Bridged Spirobi(triarylamine) Dimer with Four Perpendicularly Linked Redox‐Active π Systems

para‐Phenylene‐bridged spirobi(triarylamine) dimer 2 , in which π conjugation through four redox‐active triarylamine subunits is partially segregated by the unique perpendicular conformation, was prepared and characterized by structural, electrochemical, and spectroscopic methods. Quantum chemical calculations (DFT and CASSCF) predicted that the frontier molecular orbitals of 2 are virtually fourfold degenerate, so that the oxidized states of 2 can give intriguing electronic and magnetic properties. In fact, the continuous‐wave ESR spectroscopy of radical cation 2 ^.+ showed that the unpaired electron was trapped in the inner two redox‐active dianisylamine subunits, and moreover was fully delocalized over them. Magnetic susceptibility measurements and pulsed ESR spectroscopy of the isolated salts of 2 , which can be prepared by treatment with SbCl₅, revealed that the generated tetracation 2 ⁴⁺ decomposed mainly into a mixture of 1) a decomposed tetra(radical cation) consisting of a tri(radical cation) moiety and a trianisylamine radical cation moiety (≈75 %) and 2) a diamagnetic quinoid dication in a tetraanisyl‐p‐phenylendiamine moiety and two trianisylamine radical cation moieties (≈25 %). Furthermore, the spin‐quartet state of the tri(radical cation) moiety in the decomposed tetra(radical cation) was found to be in the ground state lying 30 cal mol^?1 below the competing spin‐doublet state.     

P2‐Na0.67AlxMn1−xO2: Cost‐Effective,Stable and High‐Rate Sodium Electrodes by Suppressing Phase Transitions and Enhancing Sodium Cation Mobility

Sodium layered P2‐stacking Na_0.67MnO₂ materials have shown great promise for sodium‐ion batteries. However, the undesired Jahn–Teller effect of the Mn⁴⁺/Mn³⁺ redox couple and multiple biphasic structural transitions during charge/discharge of the materials lead to anisotropic structure expansion and rapid capacity decay. Herein, by introducing abundant Al into the transition‐metal layers to decrease the number of Mn³⁺, we obtain the low cost pure P2‐type Na_0.67Al_xMn_1?xO₂ (x=0.05, 0.1 and 0.2) materials with high structural stability and promising performance. The Al‐doping effect on the long/short range structural evolutions and electrochemical performances is further investigated by combining in situ synchrotron XRD and solid‐state NMR techniques. Our results reveal that Al‐doping alleviates the phase transformations thus giving rise to better cycling life, and leads to a larger spacing of Na⁺ layer thus producing a remarkable rate capability of 96 mAh g^‐1 at 1200 mA g^‐1.     

Electronic Structures and Chiroptical Properties of Post‐functionalized Helicene Quinones

The synthesis of redox‐active p‐ and o‐quinones 2‐phenylamino‐4‐phenylimino[6]helicene‐1‐one 1 , 2‐phenylamino[6]‐helicene‐1,4‐dione 2 , and 4‐phenyl[6]helicene‐1,2‐dione 3 in their enantiopure forms by post‐functionalization of (P)‐ and (M)‐1,2‐dimethoxy[6]helicene is presented. Structural characterization in solution and in the solid state was accomplished by 2D NMR spectroscopy methods and X‐ray diffraction analysis, respectively. Interpretation of electrochemical redox data was accompanied by a detailed orbital picture, derived from DFT calculations. The electronic structures of compounds 1 – 3 were investigated by UV/Vis and electronic circular dichroism (ECD) spectroscopy, complemented by TD‐DFT calculations. Quinones 1 – 3 were chemically reduced to study the EPR signatures of their respective radical anions. DFT methods were used for the atom assignment of the hyperfine coupling constants. The results are discussed within the context of electrochromic chiral switches and molecular recognition.     

Excimer‐Based On‐Off Bis(pyreneamide) Macrocyclic Chemosensors

A series of bis(pyreneamide) macrocycles, synthesized in two steps from THF, THP, oxepane and 1,4‐dioxane, are tested as chemosensors for a large range of mono‐, di‐ and trivalent cations. In their native states, these macrocycles exhibit a strong excimer fluorescence that is quenched upon the addition of the metal ions (alkaline, alkaline earth, p‐, d‐, and f‐block metals). UV‐Vis spectrophotometric titrations, cyclic voltammetry, excimer fluorescence quenching, and transient absorption spectroscopy experiments helped characterize the On‐Off changes occurring upon binding and demonstrate that the highest stability constants are obtained with divalent cations Ca²⁺ and Ba²⁺ specifically.     

Co‐Conformational Isomerism in a Neutral Ion‐Paired Supramolecular System

Two different counter‐ion‐free host–guest complexes have been prepared and isolated. These compounds were formed from two equally and opposite doubly‐charged species, the viologen guests 1 a ²⁺ and 1 b ²⁺ and the anti‐disulfodibenzo[24]crown‐8 [ DSDB24C8] ^2? host, which gave rise to the 1:1 neutral complexes [ 1 a?DSDB24C8 ] and [ 1 b?DSDB24C8 ]. These species are held together by hydrogen bonding and π stacking, as well as strong electrostatic interactions. The investigation of these neutral ion‐paired supramolecular systems in solution and in the solid state allowed us to establish their co‐conformational preferences. Compound [ 1 a?DSDB24C8 ], with small methyl groups as substituents on the viologen unit, may adopt three different geometries, 1) an exo nonthreaded, 2) a partially threaded, and 3) a threaded arrangement, depending on the relative spatial orientation between the host and guest: The partially‐threaded structure is preferred in solution and in the solid state. The presence of bulky tert‐butylbenzyl groups in the viologen moiety in compound [ 1 b?DSDB24C8 ] restricts the possible geometrical arrangements to one: The exo nonthreaded arrangement. This structure was confirmed in the solid state by X‐ray crystallography. The stability of the neutral complexes in solution was determined by UV/Vis spectrophotometry. The stoichiometry of the complexes was established by continuous variation experiments, and overall equilibrium constants and ΔG° values were determined on the basis of dilution experiments. The results observed are a consequence of only the intrinsic stability of the complexes as there are no additional contributions from counter ions.     

Synthesis of Doubly Ethyl‐Bridged Bis(p‐sulfonatocalix[4]arene) and Its Supramolecular Polymerization with Viologen Dimer

A water‐soluble supramolecular polymer with a high degree of polymerization and viscosity has been constructed based on the strong host–guest interaction between p‐sulfonatocalix[4]arenes (SC4As) and viologen. A homoditopic doubly ethyl‐bridged bis(p‐sulfonatocalix[4]arene) (d‐SC4A) was prepared and its binding behavior towards methyl viologen compared with the singly ethyl‐bridged bis(p‐sulfonatocalix[4]arene) (s‐SC4A) by NMR spectroscopy and isothermal titration calorimetry. By employing a viologen dimer (bisMV⁴⁺) as the homoditopic guest, two linear AA/BB‐type supramolecular polymers, d‐SC4A?bisMV⁴⁺ and s‐SC4A?bisMV⁴⁺, were successfully constructed. Compared with s‐SC4A?bisMV⁴⁺, d‐SC4A?bisMV⁴⁺ shows much higher solubility and viscosity, and has also been characterized by viscosity, diffusion‐ordered NMR spectroscopy, dynamic light scattering, and atomic force microscopy measurements. Furthermore, the polymer is responsive to electrostimulus as viologen is electroactive, which was studied by cyclic voltammetry. This study represents a proof‐of‐principle as the polymer can potentially be applied as a self‐healing and degradable polymeric material.     

A three‐dimensional CdII coordination polymer constructed from 1,1′‐biphenyl‐2,2′,5,5′‐tetracarboxylate and 1,4‐bis(1H‐imidazol‐1‐yl)benzene ligands

The title coordination polymer, poly[[aqua(μ₅‐1,1′‐biphenyl‐2,2′,5,5′‐tetracarboxylato)bis[μ₂‐1,4‐bis(1H‐imidazol‐1‐yl)benzene]dicadmium(II)] dihydrate], {[Cd₂(C₁₆H₆O₈)(C₁₂H₁₀N₄)₂(H₂O)]·2H₂O}_n, was crystallized from a mixture of 1,1′‐biphenyl‐2,2′,5,5′‐tetracarboxylic acid (H₄bpta), 1,4‐bis(1H‐imidazol‐1‐yl)benzene (1,4‐bib) and cadmium nitrate in water–dimethylformamide. The crystal structure consists of two crystallographically independent Cd^II cations, with one of the Cd^II cations possessing a slightly distorted pentagonal bipyramidal geometry. The second Cd^II centre is coordinated by carboxylate O atoms and imidazole N atoms from two separate 1,4‐bib ligands, displaying a distorted octahedral CdN₂O₄ geometry. The completely deprotonated bpta⁴⁻ ligand, exhibiting a new coordination mode, bridges five Cd^II cations to form one‐dimensional chains viaμ₃‐η¹:η²:η¹:η² and μ₂‐η¹:η¹:η⁰:η⁰ modes, and these are further linked by 1,4‐bib ligands to form a three‐dimensional framework with a (4².6⁴)(4.6²)(4³.6⁵.7²) topology. The structure of the coordination polymer is reinforced by intermolecular hydrogen bonding between carboxylate O atoms, aqua ligands and crystallization water molecules. The solid‐state photoluminescence properties were investigated and the complex might be a candidate for a thermally stable and solvent‐resistant blue fluorescent material.     

Solvent‐Free Photooxidation of Alkanes by Dioxygen with 2,3‐Dichloro‐5,6‐dicyano‐p‐benzoquinone via Photoinduced Electron Transfer

Photooxidation of alkanes by dioxygen occurred under visible light irradiation of 2,3‐dichloro‐5,6‐dicyano‐p‐benzoquinone (DDQ) which acts as a super photooxidant. Solvent‐free hydroxylation of cyclohexane and alkanes is initiated by electron transfer from alkanes to the singlet and triplet excited states of DDQ to afford the corresponding radical cations and DDQ^??, as revealed by femtosecond laser‐induced transient absorption measurements. Alkane radical cations readily deprotonate to produce alkyl radicals, which react with dioxygen to afford alkylperoxyl radicals. Alkylperoxyl radicals abstract hydrogen atoms from alkanes to yield alkyl hydroperoxides, accompanied by regeneration of alkyl radicals to constitute the radical chain reactions, so called autoxidation. The radical chain is terminated in the bimolecular reactions of alkylperoxyl radicals to yield the corresponding alcohols and ketones. DDQ^??, produced by the photoinduced electron transfer from alkanes to the excited state of DDQ, disproportionates with protons to yield DDQH₂.     

Studies on a Vinyl Ruthenium‐Modified Squaraine Dye: Multiple Visible/Near‐Infrared Absorbance Switching through Dye‐ and Substituent‐Based Redox Processes

The bis(vinyl ruthenium)‐modified squaraine dye 1 was synthesized by treatment of [RuHCl(CO)(PiPr₃)₂] with bis(ethynyl)‐substituted squaraine 8 . Spectroscopic and electrochemical measurements on 1 and its organic precursors 6 – 8 were performed to study the effect of the vinyl ruthenium “substituents,” particularly with respect to (poly)electrochromism. Attachment of the vinyl ruthenium moieties endows metal–organic squaraine 1 with two additional oxidation waves and lowers the first two oxidation potentials by approximately 300 mV with respect to its organic precursors. Squaraines 6 , 7 , 8 , and 1 strongly absorb at 648, 663, 656, or 709 nm. Although organic dyes 6 , 7 , and 8 fluoresce, no room‐temperature emission is observed for 1 . The radical cations and anions of 6 , 7 , 8 , and 1 as well as the doubly oxidized dications have been studied by IR and UV/Vis/NIR spectroelectrochemistry, and the ?/0/+/2+ redox sequences were found to be reversible in each case. Our results indicate that the 1^2?/?/0/+/2+ redox system constitutes a polyelectrochromic switch in which absorption in the visible or the near‐infrared range is reversibly turned off or shifted deep into the NIR. They also show that radical cation 1^.+ is an intrinsically delocalized system with only little contribution from the outer vinyl ruthenium tags to the oxidation process. Dication 1²⁺ constitutes a class‐II mixed‐valent system with two electronically different vinyl ruthenium moieties and has an open‐shell singlet electronic ground‐state structure. ESR and NMR spectra of chemically prepared 1^.+ and 1²⁺ corroborate these results. It has also emerged that reduction involves an orbital that is strongly delocalized across the entire squaraine π system and strongly affects the peripheral vinyl ruthenium sites.     

Boosting Solid‐State Diffusivity and Conductivity in Lithium Superionic Argyrodites by Halide Substitution

Developing high‐performance all‐solid‐state batteries is contingent on finding solid electrolyte materials with high ionic conductivity and ductility. Here we report new halide‐rich solid solution phases in the argyrodite Li₆PS₅Cl family, Li_6?xPS_5?xCl_1+x, and combine electrochemical impedance spectroscopy, neutron diffraction, and ⁷Li NMR MAS and PFG spectroscopy to show that increasing the Cl^?/S^2? ratio has a systematic, and remarkable impact on Li‐ion diffusivity in the lattice. The phase at the limit of the solid solution regime, Li_5.5PS_4.5Cl_1.5, exhibits a cold‐pressed conductivity of 9.4±0.1 mS cm^?1 at 298 K (and 12.0±0.2 mS cm^?1 on sintering)—almost four‐fold greater than Li₆PS₅Cl under identical processing conditions and comparable to metastable superionic Li₇P₃S₁₁. Weakened interactions between the mobile Li‐ions and surrounding framework anions incurred by substitution of divalent S^2? for monovalent Cl^? play a major role in enhancing Li⁺‐ion diffusivity, along with increased site disorder and a higher lithium vacancy population.     

A new oxidation state of aniline pentamer observed in water‐soluble electroactive oligoaniline‐chitosan polymer

A novel water‐soluble electroactive polymer, aniline pentamer crosslinked chitosan (Pentamer‐c‐Chi), was prepared by condensation polymerization of the terminal carboxyl groups in aniline pentamer with the amino side groups in chitosan in aqueous solution. The carboxyl groups were activated by N‐hydroxysuccinimide (NHS) and N,N′‐dicyclohexylcarbodiimide (DCC). The electrochemical behavior of anilinepentamer in this kind of crosslinked polymer was studied in acidic aqueous solution by means of cyclic voltammetry (CV), UV–vis, and electron spin resonance (ESR) spectroscopy. There were three reversible redox peaks in the CV of Pentamer‐c‐Chi. A new emeraldine oxidization state in the form of radical cations was proposed, which was associated with the new absorption band at 370 nm in the UV–vis spectra. The ESR of the aqueous solution of Pentamer‐c‐Chi showed a single Lorentzian shaped signal, which suggested the existence of radical cations. The new redox state was pH dependent and appeared only at pH < 3. The stability of radical cations could be attributed to the hydrogen bonds between radical cations, water, and chitosan. Morphological structure of the Pentamer‐c‐Chi can be adjusted by varying the content of aniline pentamer. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1124–1135, 2008     

Photoinduced Electron Transfer within a Zinc Porphyrin–Cyclobis(paraquat‐p‐phenylene) Donor–Acceptor Dyad

Understanding the mechanism of efficient photoinduced electron‐transfer processes is essential for developing molecular systems for artificial photosynthesis. Towards this goal, we describe the synthesis of a donor–acceptor dyad comprising a zinc porphyrin donor and a tetracationic cyclobis(paraquat‐p‐phenylene) (CBPQT⁴⁺) acceptor. The X‐ray crystal structure of the dyad reveals the formation of a dimeric motif through the intermolecular coordination between the triazole nitrogen and the central Zn metal of two adjacent units of the dyad. Photoinduced electron transfer within the dyad in MeCN was investigated by femtosecond and nanosecond transient absorption spectroscopy, as well as by transient EPR spectroscopy. Photoexcitation of the dyad produced a weakly coupled ZnP^+.–CBPQT^3+. spin‐correlated radical‐ion pair having a τ=146 ns lifetime and a spin–spin exchange interaction of only 0.23 mT. The long radical‐ion‐pair lifetime results from weak donor–acceptor electronic coupling as a consequence of having nine bonds between the donor and the acceptor, and the reduction in reorganization energy for electron transfer caused by charge dispersal over both paraquat units within CBPQT^3+..     

An Organic Mixed‐Valence Ligand for Multistate Redox‐Active Coordination Networks

The multistate redox‐active/multi‐interactive ligand 5,5′,8,8′‐tetra(4‐pyridyl)‐2,2′‐(1,4‐phenylene)bis‐1H‐perimidine (H₂TPP) was designed and synthesized. H₂TPP undergoes four one‐electron oxidation steps, and was used for the preparation of a multistate redox‐active coordination network in a solid–liquid interface reaction using molten Cd²⁺ salts. The multiple redox states of H₂TPP were confirmed spectroscopically by stepwise four‐electron oxidation. Spectroscopic analysis indicated that the mixed‐valence states of the ligand are class II on the UV/Vis/NIR timescale and borderline class II/class III on the ESR timescale.     

Aggregation‐Induced Emission‐Active 1,4‐Dihydropyridine‐Based Dual‐Phase Fluorescent Sensor with Multiple Functions

A N‐2‐phenylethyl‐substituted 1,4‐dihydropyridine derivative (NDHP) containing 5,5‐dimethylcyclohexane‐1,3‐dione and naphthylethylene was designed and synthesized. NDHP acts as a multifunctional fluorescent sensor in dual phases. The crystal structure analysis confirms that the NDHP molecules have highly twisted conformations. The twisted conformation results in aggregation‐induced emission properties and solid‐state emission, by restricting the intramolecular free rotation in the aggregated or solid state. In the solid state, NDHP exhibits reversible mechanochromic properties as a result of the transition between the amorphous and crystalline states. NDHP also exhibits a rare phenomenon of acid‐fumed solid‐state emission enhancement owing to the change in packing mode from a zigzag arrangement to J‐aggregation. The solid‐state stimuli‐responsive fluorescence switching is applied to realize a rewritable optical recording media and a multiple output combinational logic system. In solution, NDHP shows a selective fluorescence response for environmentally harmful Hg²⁺, with a limit of detection of 2.7 nm . This results from the “turn‐on” responsive behavior owing to the Hg²⁺‐triggered aggregation of the NDHP molecules. NDHP is also used in the imaging of intracellular Hg²⁺ in HeLa cells. These findings provide a feasible and attractive route for developing multifunctional fluorescent sensors for use in dual phases.     

Poly[hexaaquaocta‐μ3‐hydroxido‐tetrakis(μ3‐methylenedisulfonato)‐μ6‐oxido‐hexaytterbium(III)]: the first lanthanide sulfonate containing a hexanuclear Ln–hydroxide/oxide cluster synthesized via `ligand‐controlled acidolysis' of lanthanide oxide

The combination of redox and acid sites in lanthanide sulfonate leads to a potentially multifunctional catalyst for oxidation reactions. The title lanthanide sulfonate compound, [Yb₆(CH₂O₆S₂)₄O(OH)₈(H₂O)₆]_n, exhibits a novel one‐dimensional columnar structure along the a direction. In the building unit of the columnar oligomer, a face‐capped lanthanide octahedron, viz. [Ln₆(μ₆‐O)(μ₃‐OH)₈]⁸⁺, is found with an interstitial μ₆‐oxide group lying on an inversion centre, reports of which are rare in the literature. Adjacent hexameric cations are connected via two pairs of O—S—O bridges, thus forming a neutral column. The three‐dimensional network is stabilized by an intricate pattern of intercolumnar hydrogen bonds.     

Radical‐Cation Dimerization Overwhelms Inclusion in [n]Pseudorotaxanes

Suppression of the dimerization of the viologen radical cation by cucurbit[7]uril ( CB7 ) in water is a well‐known phenomenon. Herein, two counter‐examples are presented. Two viologen‐containing thread molecules were designed, synthesized, and thoroughly characterized by ¹H DOSY NMR spectrometry, UV/Vis absorption spectrophotometry, square‐wave voltammetry, and chronocoulometry: BV ⁴⁺, which contains two viologen subunits, and HV ¹²⁺, which contains six. In both threads, the viologen subunits are covalently bonded to a hexavalent phosphazene core. The corresponding [3]‐ and [7]pseudorotaxanes that form on complexation with CB7 , that is, BV ⁴⁺?( CB 7)₂ and HV ¹²⁺?( CB 7)₆, were also analyzed. The properties of two monomeric control threads, namely, methyl viologen ( MV ²⁺) and benzyl methyl viologen ( BMV ²⁺), as well as their [2]pseudorotaxane complexes with CB7 ( MV ²⁺? CB7 and BMV ²⁺? CB7 ) were also investigated. As expected, the control pseudorotaxanes remained intact after one‐electron reduction of their viologen‐recognition stations. In contrast, analogous reduction of BV ⁴⁺?( CB 7)₂ and HV ¹²⁺?( CB 7)₆ led to host–guest decomplexation and release of the free threads BV ^{2( . +)} and HV ^{6( . +)}, respectively. ¹H DOSY NMR spectrometric and chronocoulometric measurements showed that BV ^{2( . +)} and HV ^{6( . +)} have larger diffusion coefficients than the corresponding [3]‐ and [7]pseudorotaxanes, and UV/Vis absorption studies provided evidence for intramolecular radical‐cation dimerization. These results demonstrate that radical‐cation dimerization, a relatively weak interaction, can be used as a driving force in novel molecular switches.     

Stabilization of [WF5]+ by Bidentate N‐Donor Ligands

Transition‐metal hexafluorides do not exhibit fluoride‐ion donor properties in the absence of donor ligands. We report the first synthesis of donor‐stabilized [MF₅]⁺ derived from a transition‐metal hexafluoride via fluoride‐ion abstraction using WF₆(L) (L=2,2′‐bipy, 1,10‐phen) and SbF₅(OSO) in SO₂. The [WF₅(L)][Sb₂F₁₁] salts and [WF₅(1,10‐phen)][SbF₆]?SO₂ have been characterized by X‐ray crystallography, Raman spectroscopy, and multinuclear NMR spectroscopy. The reaction of WF₆(2,2′‐bipy) with an equimolar amount of SbF₅(OSO) reveals an equilibrium between [WF₅(2,2′‐bipy)]⁺ and the [WF₄(2,2′‐bipy)₂]²⁺ dication, as determined by ¹⁹F NMR spectroscopy. The geometries of the cations in the solid state are reproduced by gas‐phase geometry optimizations (DFT‐B3LYP), and NBO analyses reveal that the positive charges of the cations are stabilized primarily by compensatory σ‐electron donation from the N‐donor ligands.     

Copolymerization of poly(vinyl alcohol)‐graft‐poly(1,4‐dioxan‐2‐one) with designed molecular structure by a solid‐state polymerization method

Poly(vinyl alcohol)‐graft‐poly(1,4‐dioxan‐2‐one) (PVA‐g‐PPDO) with designed molecular structure was synthesized by a solid‐state polymerization. The solid‐state copolymerization was preceded by a graft copolymerization of PDO initiated with PVA as a multifunctional initiator, and Sn (Oct)₂ as a coininitiator/catalyst in a homogeneous molten state. The polymerization temperature was then decreased and the copolymerization was carried out in a solid state. The products prepared by solid‐state polymerization were characterized by ¹H NMR and DSC, and were compared with those synthesized in the homogeneous molten state. The degree of polymerization (D_p), degree of substitution (D_s), yield and the average molecular weight of the graft copolymer with different molecular structure were calculated from the ¹H NMR spectra. The results show that the crystallization process during the solid‐state polymerization may suppress the undesirable inter‐ or intramolecular side reactions, then resulting in a controlled molecular structure of PVA‐g‐PPDO. The results of DSC measurement show that the molecular structures determine the thermal behavior of the PVA‐g‐PPDO. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3083–3091, 2006