Unsaturated polyesters are synthesized via ring‐opening copolymerization of α‐methylene‐δ‐valerolactone and δ‐valerolactone. These polyesters 4a–c are mixed with ethyl methacrylate (EMA), 2‐hydroxyethyl methacrylate (HEMA), and α‐methylene‐δ‐valerolactone (α‐MVL), respectively. Then, crosslinking is carried out by free radical polymerization initiated by an azo‐initiator. A second glass transition is found with incorporation of HEMA and α‐MVL. These findings indicate the formation of phase‐separated polyester blocks crosslinked with the poly(meth)‐acrylic‐segments, respectively poly(α‐methylene‐δ‐valerolactone) segments.
Synthesis of a multiblock copolymer composed of cis‐1,4‐polybutadiene (PBd) segments and poly(3‐buten‐1‐ol) segments is performed via successive hydroboration and oxidation of cis‐1,4/syn‐1,2‐multiblock PBd. The ratio of functionalization can be controlled by changing the amount of the borane reagent. The obtained polymer shows two distinctive glass‐transition temperatures, which correspond to the cis‐1,4‐PBd block and the poly(3‐buten‐1‐ol) block. These thermal properties clearly show that the functionalization of the PBd proceeds keeping the elastic property derived from cis‐1,4 segment.
Comb‐like copolymers based on a polyolefin backbone of poly(10‐undecene‐1‐ol) (PUol) with poly(ε‐caprolactone) (PCL) side chains are synthesized in two steps. After synthesis of PUol by metallocene‐catalyzed polymerization, the side‐chain hydroxyl functionalities of this polar polyolefin are used as an initiator for the ring‐opening polymerization (ROP) of ε‐caprolactone (CL). In this context, copolymers with different lengths of PCL grafts are prepared. The chemical structure and the composition of the synthesized copolymers are characterized by 1H and 13C NMR spectroscopy. It is shown that the hydroxyl end groups of PUol act effectively as initiating sites for the CL ROP. Size‐exclusion chromatography (SEC) measurements confirm the absence of non‐attached PCL and the expected increase in molar mass after grafting. The thermal and decomposition behaviors are investigated by DSC and thermogravimetric analysis (TGA). The effect of the length of the PCL grafts on the crystallization behavior of the comb‐like copolymers is investigated by DSC and wide‐angle X‐ray scattering (WAXS).
In this paper, “star anise”‐like anisotropic micelle (AM) from direct aqueous self‐assembly of poly(ethylene oxide)‐block‐poly(p‐dioxanone) amphiphilic diblock copolymer is presented. By adding poly(ethylene imine) (PEI), the AM shows morphological change from “star anise” to swollen sphere. The mechanism of PEI‐triggered morphological transition involving complexation and weakening of crystallizability is revealed.
Core–corona inversion of micelles of diblock copolymer poly(acrylic acid)‐block‐poly(N‐isopropylacrylamide) (PAA‐b‐PNIPAM), has been successfully realized by switching either pH or temperature. The strong interaction of doxorubicin with the PAA block and the pH‐sensitive drug release from the polymer make the system very useful as a controlled drug delivery system. The encapsulation of hydrophobic Nile Red molecules above the lower critical solution temperature of PNIPAM suggests that this polymer may be useful for removing hydrophobic pollutants.
The preparation and study of a new poly(3‐alkyloxythiophene)—bearing a chiral center—is presented, with particular reference to the evolution of optical activity in passing from solution to solid state. The combination of optical analysis, electronic circular dichroism, and X‐ray diffraction of powders or films supplies strong indications of a possible use of this material as an inverse chiral probe.
A novel polymerization mechanism transformation strategy, involving anionic ring‐opening polymerization and photoinduced cationic polymerization, is successfully applied for the synthesis of poly(ethylene oxide)‐graft‐poly(isobutyl vinyl ether) (PEO‐g‐PIBVE). First, poly(ethylene oxide‐co‐ethoxyl vinyl glycidyl ether) [P(EO‐co‐EVGE)] is synthesized by living anionic polymerization. The vinyl moieties of the functional PEO‐based polymer are converted to the hydrogen iodide adduct by photolysis of diphenyliodonium iodide, monitored using NMR spectroscopy. A modified mode of Lewis acid‐catalyzed living cationic polymerization is performed as a “grafting from” method to generate PIBVE segments grafted onto the PEO main chain. Both the intermediates and the final graft copolymers are characterized by gel‐permeation chromatography (GPC) and 1H NMR analysis.
Four‐arm poly(l ‐2‐hydroxybutanoic acid) [P(L‐2HB)]/poly(d ‐lactic acid) (PDLA) blends are phase‐separated to form P(L‐2HB)‐rich and PDLA‐rich domains. Hetero‐stereocomplex (HTSC) crystallization should occur at the interface of two types of domains. The crystallization temperature ranges, wherein HTSC crystallites, P(L‐2HB), and PDLA homocrystallites are crystallizable in the star‐shaped 4‐arm P(L‐2HB)/PDLA blends, are much narrower than those reported for linear 1‐arm P(L‐2HB)/PDLA blends, indicating that the star‐shaped architecture disturbs the isothermal crystallization of the blends. Exclusive HTSC crystallization is not observed for the star‐shaped 4‐arm blends during isothermal crystallization in marked contrast with the result reported for the linear 1‐arm blends.
Lamellar bending habits, as influenced by molecular‐chain chirality, in packing into dendritic spherulites with specific optical patterns are discussed using two model polymers of opposite chirality that are blended with a common polymer as examples: i) poly(l ‐lactic acid)/poly(butylene adipate) (PLLA/PBA) and ii) poly(d ‐lactic acid)/PBA (PDLA/PBA) blends. The bending habits in the spherulites of PLLA or PDLA blended with PBA are dictated by the chirality, specifically the counterclockwise and clockwise directions for the PLLA/PBA (50:50) and PDLA/PBA (50:50) blends, respectively. Straight lamellae in spiral lozenge crystals are packed with crystal aggregates of PLLA on top of the flat‐on lamellae plates acting as a basal plane during crystallization at Tc; spiral lozenge‐crystal frameworks are surrounded by needle‐like crystals resembling PBA crystals.
Poly(methyl methacrylate)‐block‐poly(4‐vinylpyridine), polystyrene‐block‐poly(4‐vinyl pyridine), and poly(ethylene glycol)‐block‐poly(4‐vinylpyridine) block copolymers are synthesized by successive atom transfer radical polymerization (ATRP), single‐electron‐transfer nitroxide‐radical‐coupling (SET‐NRC) and nitroxide‐mediated polymerization (NMP). This paper demonstrates that this new approach offers an efficient method for the preparation of 4‐vinylpyridine‐containing copolymers.
Highly monodisperse poly(2‐hydroxyethyl acrylate)‐grafted poly(methyl methacrylate) (PMMA) microspheres are prepared by a facile photoinitiated dispersion polymerization in ethanol/water mixtures at room temperature. Poly(2‐hydroxyethyl acrylate) homopolymers with different molecular weights are synthesized via reversible addition‐fragmentation chain transfer (RAFT) solution polymerization and employed as steric stabilizers in photoinitiated dispersion polymerization. The effect of macro‐RAFT agent (both concentration and molecular weight) on particle diameter is studied in detail. Kinetic study indicates that the polymerization proceeded rapidly with 96% yield being reached with 1 h of UV irradiation. Finally, the obtained hydroxyl‐rich PMMA microspheres are used as building blocks for the preparation of covalently cross‐linked colloidosomes.
The synthesis of high‐aspect‐ratio (AR) CdSe (NRs) nanorods and their ordered assembly over large areas are reported. Long‐range ordering of hexagonal arrays of high‐AR NRs is achieved by a combination of controlled solvent evaporation and the use of an applied electric field. Vertically oriented assemblies of CdSe NRs functionalized with oligo‐ and polythiophene are also obtained. Aligned and oriented polythiophene CdSe NRs have potential applications in organic–inorganic hybrid bulk‐heterojunction photovoltaic devices.
Nonionic aliphatic polymers containing ester and sulfonyl moieties, [poly(ester‐sulfones)s] were found to undergo anode‐selective electrophoresis under electrophoretic deposition conditions. Herein are reported the syntheses of unsaturated nonionic polyesters containing sulfide linkages and double bonds on the polymer backbone via acyclic diene metathesis polymerization using a Grubbs' catalyst. Subsequent oxone oxidation was carried out, affording the corresponding poly(ester‐sulfone), followed by electrophoretic deposition of the unsaturated poly(ester‐sulfone) onto stainless steel. Subsequent UV‐irradiation cured the deposited film, improving the peeling strength of the coating.
Low‐field NMR relaxometry is sensitive to molecular mobility within well‐defined time windows and can thus be applied to study interactions between polymers and inorganic filler particles in composite materials. Volume fraction and dispersion of the filler influence the polymer chain dynamics, which also modify the macroscopic properties of the polymer composites. As model systems, TiO2‐filled poly(n‐alkyl methacrylates) with different side‐chain lengths and filler contents are prepared by melt mixing. Several 1H NMR relaxation parameters, which are sensitive and selective toward polymer–filler interactions, are investigated at a Larmor frequency of 20 MHz as a function of temperature. Both physical and empirical models are used to analyze the NMR data, and the results are compared with the aim of an unambiguous detection of polymer–filler interactions.
A size exclusion chromatography (SEC)‐gradient method is developed allowing poly(n‐butyl acrylate‐stat‐acrylic acid)s to be separated with respect to content of acrylic acid over the complete composition range. After setting up the chromatographic method, samples that, according to the amounts of charged monomers, are expected to have identical chemical composition are compared. The chromatograms reveal differences in elution volume, which, by 1H NMR spectroscopy, can be partially traced back to differences in polymer composition. In addition, samples of similar compositions prepared in different solvents exhibit differences in chemical composition distribution.
The combination of ring‐opening metathesis polymerization (ROMP) and copper‐catalyzed azide–alkyne cycloaddition (CuAAC) is described as an efficient click reaction to synthesize a new range of well‐defined comb‐like polynorbornene/polyoxanorbornene graft copolymers containing poly(ethylene glycol) (PEG) and/or poly(ε‐caprolactone) (PCL) as side chains. The “grafting through” method is applied for the synthesis of polyoxanorbornene‐g‐PEG via ROMP of oxanorbornenyl di‐PEG macromonomer prepared by click coupling of azide‐terminated PEG with di‐alkyne‐functionalized oxanorbornene. The well‐characterized macromonomer is then subjected to ROMP. Polynorbornene‐g‐PCL and polynorbornene‐g‐PEG are prepared by the “grafting onto” route. This is achieved by ROMP of 5‐bromohexyloxymethyl norbornene followed by reaction with NaN3 and then click reaction with alkyne‐terminated PEG and PCL. (Polyoxanorbornene‐g‐PEG)‐ran‐(polynorbornene‐g‐PCL) is prepared by ROMP of a mixture of oxanorbornenyl di‐PEG and 5‐bromohexyloxymethyl norbornene followed by reaction with NaN3 and subsequently click reaction with alkyne‐end‐capped PCL. All intermediates and final products are characterized by IR, NMR, MS, and size exclusion chromatography (SEC). Self‐assembly of these comb‐like polymers in solution into micro/nanostructures is foreseen, leading to a wide range of potential applications.
The effect of thermal treatment on the transition of molecular packing and orientation of the semiconducting poly(2,5‐dihexyloxy‐p‐phenylene) (PPP) film is probed by the combination of in situ 2D grazing incidence X‐ray diffraction (2D GIXD) and selected area electron diffraction (SAED). The structure analysis indicates that PPP crystallizes in an orthorhombic unit cell with a = 21.20 Å, b = 3.78 Å, and c = 4.24 Å. A variation of the annealing temperature from 80 °C to 100 °C demonstrates that the worm‐like morphology in the pristine film melts and develops into nanowires. Furthermore, the molecular orientation transforms from face‐on to edge‐on via thermal annealing. Remarkably, a previously unknown metastable state of “slope” edge‐on with a tilt angle of 51.1° is observed. This orientation change arises from the heterogeneous nucleation and growth of edge‐on PPP crystal during crystallization from the melt.
Nanostructures of stereocomplex polylactide (sc‐PLA) are obtained and studied in poly(l ‐lactide) (PLLA) doped with a low amount of poly(d ‐lactide) (PDLA) during successive melt‐quenching, extrusion, spinning, and drawing processes corresponding to quiescent, shear flow, elongational flow, and tensioned annealing conditions, respectively. Nanogranules of predominantly sc‐PLA are initially formed with rapid quenching in quiescent and shear flow, which developed into microspheres with slow quenching and uniform nanofibrils in elongational flow. While only amorphous or the α′‐form PLLA is formed with the quenched melts and macroscopic fibers, the embedded nanogranules and nanofibrils are highly crystallized with the coexistence of sc‐PLA and the α‐crystals. A 1D coalescence of nascent sc‐nuclei into nanofibrils in elongational flow is preliminarily proposed to explain the structure evolution and the minor reinforcement of the nanofibrils on the macroscopic fibers.
A facile surface modification procedure for electrospun poly(butylene terephthalate) (PBT) fibers by surface‐initiated atom transfer radical polymerization (SI‐ATRP) is reported. Initiators are introduced through aminolysis and chemical vapor adsorption. SI‐ATRP is subsequently carried out to prepare a polymer‐grafted layer at the PBT fiber surface without altering the fiber geometry. After modification with a zwitterionic poly(sulfobetaine), poly(3‐(N‐2‐methacryloyloxyethyl‐N,N‐dimethyl) ammonatopropanesulfonate), the surface is superhydrophilic. The surface properties are thermally stable due to the high melting temperature of the PBT crystallites and are maintained for a prolonged period.
In this study, it is found that amylose stereoselectively includes poly(d ‐alanine) in the polyalanine stereoisomers in vine‐twining polymerization to form the corresponding inclusion complex, a novel saccharide–peptide supramolecular conjugate. The vine‐twining polymerization is performed by thermostable phosphorylase‐catalyzed enzymatic polymerization, which produces amylose, in the presence of poly(d ‐alanine), poly(l ‐alanine), or poly(dl ‐alanine) dispersed in aqueous buffer solvent. The X‐ray diffraction and 1H NMR measurements of the products indicate that the inclusion complex is formed from poly(d ‐alanine), whereas the systems using the other stereoisomers do not induce the inclusion complexation. The analytical results and the guest exchange experiment suggest the that average molecular ratio of amylose to poly(d ‐alanine) is 1:1, and the host cavity is partially occupied by the guest.
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