Processive rotaxane systems. Studies on the mechanism and control of the threading process

The threading behavior of a zinc analogue of a previously reported processive manganese porphyrin catalyst onto a series of polymers of different lengths is reported. It is demonstrated that the speed of the threading process is determined by the opening of the cavity of the toroidal porphyrin host, which can be tuned with the help of axial ligands that coordinate to the metal center in the porphyrin.     

动态力学温度谱分析的新方法及其应用 Ⅳ.从动态力学温度谱求两相聚合物的双活化能和应力松弛

提出用两个热流变简单粘弹体的并联体系作为两相聚合物的粘弹模型,将先前的动态力学温度谱分析方法推广到两相聚合物中去.运用这种新方法从动态力学数据求出了PET/70PHB共聚物的双活化能,其中150℃左右的转变活化能为71.9kcal/mol,70℃左右的转变活化能为117.5koal/mol,这一数值与文献上PET/60PHB这个转变的活化能120kcal/mol相接近.文中还计算了共聚物在不同温度下的10s应力松弛模量,所得结果与实测值相吻合.     

Precise synthesis of porphyrin array scaffolding polyisocyanides

Aryl isocyanides bearing free‐base and metallo‐porphyrins were prepared and polymerized with a Pd–Pt μ‐ethynediyl complex as the initiator to give polymers with narrow polydispersity indices. The molecular weights of the resulting polymers were precisely controlled by the initial feed ratio of the porphyrin monomer to the initiator. The UV–VIS spectra suggested that the porphyrin pendants are regularly arranged to form stacked columns. Metallo‐porphyrin polymers were also prepared by reacting free‐base porphyrin polymers with metal salts. The successive reactions of free‐base and zinc‐porphyrin monomers resulted in the formation of diblock polymers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 585–595, 2006     

Syntheses and reactions of porphyrin and metalloporphyrin polymers

Various porphyrin functions such as protoporphyrin IX and chlorin a as well as metalloporphyrin functions such as Mg(II)– and Cu(II)–chlorophyllin a and Fe(III)– and Co(II)–protoporphyrin IX were incorporated into vinyl polymers by preparation and polymerization of their p-vinylbenzyl esters. The porphyrin function was also incorporated by reaction of poly-p-chloromethylstyrene with porphyrins or metalloporphyrins or by the reaction of p-aminostyrene polymers with chlorophyll b through Schiff-base formation. Mg(II)–porphyrin polymers were found to be remarkably effective as catalysts in photoredox systems; porphyrin polymers without central metal atoms were also effective to a lesser extent.     

Poly(hydroxybutyrate) and epichlorohydrin elastomers blends: Phase behavior and morphology

This work studied blends of PHB with epichlorohydrin elastomers, the PEP homopolymer and its copolymer with ethylene oxide, ECO. PHB is a microbial polyester, which is accumulated intracellularly by a large number of microorganisms, presenting characteristics of biodegradability and biocompatibility. It presents a high degree of crystallinity, so is a quite brittle material, and may undergo degradation when is kept for a relatively short time at a temperature above its melting point, about 180 °C. PEP and ECO are linear and amorphous elastomers, exhibit miscibility with many aliphatic polyesters and these elastomers have been used in various branches of technology, such as the automotive industry. The proposed systems combine a polymer with high crystallinity and biodegradability, PHB, with amorphous epichlorohydrin elastomers. Blends were prepared by casting from chloroform solution at different compositions (0, 20, 40, 50, 60, 80 and 100 wt% of PHB). The phase behavior of PHB/PEP and PHB/ECO blends were studied by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and the morphology of the crystalline phase of PHB had been examined by optical microscopy. Blends of PHB/PEP and PHB/ECO have been described in literature as miscible. However, our results from the DSC and DMA show that PHB/PEP and PHB/ECO blends are immiscible. This behavior should be related to the molecular weight of polymers used in the present work, which is higher than the molecular weight of polymers used in the previous works. The crystallization kinetics of PHB is strongly influenced by the presence of the elastomeric phase. The degree of crystallinity of PHB/PEP blends decreases with an increase in the PEP content. PHB/ECO blends present degrees of crystallinity that can be considered nearly independent of the ECO content. Differences in the morphology of the crystalline phase were also observed, and these are attributed to the presence of elastomeric phase in the intraspherulitic zone.     

The effect of melt-processing on the degradation of selected polyhydroxyacids: polylactides, polyhydroxybutyrate, and polyhydroxybutyrate-co-valerates

A series of resorbable polyhydroxyacids were studied by size exclusion chromatography (SEC), viscosity measurements, and differential scanning calorimetry (DSC) for the effect of the injection moulding process on the molecular weight and thermal properties of the polymers. The polymers studied were polylactides (PLA), polyhydroxybutyrate (PHB) and polyhydroxybutyrate-co-valerate (PHB/VA) (5–22% VA content). All polylactides underwent extensive degradation, in the range of 50–88%, and an increase in molecular weight distribution (MWD) following injection moulding at temperatures ranging from 130 to 215°C. In contrast to the polylactides, the decrease in molecular weight of the PHB and PHB/VA polymers after injection moulding at temperatures from 135 to 160°C was less dramatic, in the range of 4–53%. This was accompanied by a decrease of the MWD. No evidence for low molecular weight non-volatile degradation products was observed. Injection moulding led to a decrease in the melting temperature (T_m) and the heat of melting (ΔH_m) of PLA. Conversely, the moulding process did not significantly affect the melting temperature and heat of melting of polyhydroxybutyrate/valerates.     

Synthesis of dendron-protected porphyrin wires and preparation of a one-dimensional assembly of gold nanoparticles chemically linked to the pi-conjugated wires

A one-dimensional assembly of gold nanoparticles chemically bonded to pi-conjugated porphyrin polymers was prepared on a chemically modified glass surface and on an undoped naturally oxidized silicon surface by the following methods: pi-conjugated porphyrin polymers were prepared by oxidative coupling of 5,15-diethynyl-10,20-bis-((4-dendron)phenyl) porphyrin (6), and its homologues (larger than 40-mer) were collected by analytical gel permeation chromatography (GPC). The porphyrin polymers (>40-mer) were deposited using the Langmuir-Blodgett (LB) method on substrate surfaces, which were then soaked in a solution of gold nanoparticles (2.7 +/- 0.8 nm) protected with t-dodecanethiol and 4-pyridineethanethiol. The topographical images of the surface observed by tapping mode atomic force microscopy (AFM) showed that the polymers could be dispersed on both substrates, with a height of 2.8 +/- 0.5 nm on the modified glass and 3.1 +/- 0.5 nm on silicon. The height clearly increased after soaking in the gold nanoparticle solution, to 5.3 +/- 0.5 nm on glass and 5.4 +/- 0.7 nm on silicon. The differences in height (2.5 nm on glass and 2.3 nm on silicon) corresponded to the diameter of the gold nanoparticles bonded to the porphyrin polymers. The distance between gold nanoparticles observed in scanning electron microscopic images was ca. 5 nm, indicating that they were bonded at every four or five porphyrin units.     

Synthesis and Characterization of One-dimensional and Two-Dimensional Porphyrin Polymers (Ⅰ)

Porphyrin polymers are of interest in relation to conductive materials[1, 2], catalysts for photosynthetic charge separation[3], or the fundamental features in biological systems[4]. There have been many versatile studies about them[5.6]. The one-dimensional "Shish Kebab"porphyrin polymers synthesized with a new method different from those reported and Schiff-base porphyrin polymers with two-dimensional nano-structure have provided a new field of study. The present paper covers highly ordered…     

Oligopyrenotides: chiral nanoscale templates for chromophore assembly

Getting organized: DNA-like supramolecular polymers formed of short oligopyrenotides serve as a helical scaffold for the molecular assembly of ligands. The cationic porphyrin meso-tetrakis(1-methylpyridin-4-yl)porphyrin interacts with the helical polymers in a similar way as with poly(dA:dT).     

Synthesis and Optical Properties of Dendronized Porphyrin Polymers

Summary: A novel kind of dendronized porphyrin polymers was synthesized by Sonogashira coupling of diethynyl‐functionalized porphyrin monomers and diiodo‐functionalized macromonomers bearing Fréchet‐type dendrons. The encapsulation of red‐light‐emitting porphyrin‐containing conjugated backbones into dendronized polymers can not only reduce the aggregation of polymer backbones and the self‐quenching of their fluorescence but also endow the porphyrin polymers with good solubility. We also report the optical and electrochemical properties of the porphyrin‐containing dendronized polymers.

Synthesis of a novel kind of dendronized porphyrin polymers by Sonogashira coupling of diethynyl‐functionalized porphyrin monomers and diiodo‐functionalized dendritic macromonomers.     

Multiple melting behaviour of poly(3-hydroxybutyrate-co-hydroxyvalerate) using step-scan DSC

Melting behaviour and crystal morphology of poly(3-hydroxybutyrate) (PHB) and its copolymer of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with various hydroxyvalerate (HV) contents [5 wt.% (PHB5V), 8 wt.% (PHB8V) and 12 wt.% (PHB12V)] have been investigated by conventional DSC, step-scan differential scanning calorimetry (SDSC), wide angle X-ray diffraction (WAXRD) and hot stage polarised optical microscopy (HSPOM). Crystallisation behaviour of PHB and its copolymers were investigated by isothermal crystallisation kinetics. Thermal properties were investigated after isothermal crystallisation treatment. Multiple melting peak behaviour was observed for all polymers. SDSC data revealed that PHB and its copolymers undergo melting-recrystallisation-remelting during heating, as evidenced by exothermic peaks in the IsoK baseline (C_p,IsoK, non-reversing signal). An increase in degree of crystallinity due to significant melt-recrystallisation was observed for isothermally crystallised polymers. SDSC proved a convenient and precise method for measurement of the apparent thermodynamic specific heat (C_p,ATD, reversing signal). PHB and PHBV showed different crystal morphologies for similar crystallisation condition. HSPOM results showed that the crystallisation rates reduced and sizes of spherulites were significantly increased as HV content increased.     

Model-Based Nutrient Feeding Strategies for the Increased Production of Polyhydroxybutyrate (PHB) by <Emphasis Type="Italic">Alcaligenes latus</Emphasis>

Polyhydroxyalkanoates (PHAs) are biodegradable polymers which are considered as an effective alternative for conventional plastics due to their mechanical properties similar to the latter. However, the widespread use of these polymers is still hampered due to their higher cost of production as compared to plastics. The production cost could be overcome by obtaining high yields and productivity. The goal of the present research was to enhance the yield of polyhydroxybutyrate (PHB) with the help of two simple fed-batch cultivation strategies. In the present study, average batch kinetic and substrate limitation/inhibition study data of Alcaligenes latus was used for the development of PHB model which was then adopted for designing various off-line nutrient feeding strategies to enhance PHB accumulation. The predictive ability of the model was validated by experimental implementation of two fed-batch strategies. One such dynamic strategy of fed-batch cultivation under pseudo-steady state with respect to nitrogen and simultaneous carbon feeding strategy resulted in significantly high biomass and PHB concentration of 39.17 g/L and 29.64 g/L, respectively. This feeding strategy demonstrated a high PHB productivity and PHB content of 0.6 g/L h and 75%, respectively, which were remarkably high in comparison to batch cultivation. The mathematical model can also be employed for designing various other nutrient feeding strategies.     

Novel water-soluble photosensitizer based on starch and containing porphyrin

Novel water-soluble polymeric photosensitizers (SPO) based on starch and containing porphyrin chromophores were synthesized and studied. The polymers were soluble in water and in dimethyl sulfoxide. Photophysical studies and solubilization of molecular probes proved the formation of hydrophobic, rigid microdomains in an aqueous solution of SPO; they were created due to the clustering of porphyrin chromophores attached to the polymer chain. SPO polymers absorbed light from the UV-visible spectral region. The polymers could sensitize photochemical reactions mediated by electron transfer, energy transfer or both, from the singlet-excited state of porphyrin chromophores to the molecules of organic compounds solubilized in the hydrophobic microdomains or residing in the water phase.     

水体系中含卟啉基团的两亲高分子的自组装行为和性质的研究

在文中合成了两种不同的卟啉单体5-(4-acryloyloxyphenyl)-10,15,20-tris(4-carboxylphenyl)porphyrinate zinc(Ⅱ)(ZnAOTCPP)和5-(4-acrylo-yloxyphenyl)-10,15,20-tris(4-methoxycarboxylphenyl)porphyrinate zinc(Ⅱ)(ZnMeAOTCPP),它们分别与丙烯酰胺(Acrylamide,AM)聚合得到含有卟啉基团的两亲高分子.与对应的单体相比,含有三羧酸卟啉基团的高分子在水中形成了一个新的紫外吸收峰和一个新的荧光发射峰,而含有三羧酸甲酯卟啉基团的高分子除此之外在更长波的方向上还另外出现了一个新的紫外吸收峰和一个新的荧光发射峰.随着高分子水溶液浓度的提高,高分子中卟啉基团的光谱性质的变化趋势显示高分子在水中的自组装行为可以分为分子间缔合和分子内缔合的两种情况.此外,实验结果显示含有三羧酸甲酯卟啉基团的高分子相对于含有三羧酸卟啉基团的高分子更加有利于卟啉缔合物的形成.     

Synthesis of PHB nanoparticles from optimized medium utilizing dairy industrial waste using Brevibacterium casei SRKP2: A green chemistry approach

Polyhydroxyalkanoates (PHAs) are natural, biodegradable polymers accumulated by bacteria under nutritional exhausted condition where carbon source is in excess. A gram positive bacterium (designated strain SRKP2) that potentially accumulated polyhydroxybutyrate (PHB) was isolated from dairy industrial waste. From its morphological and physiological properties and nucleotide sequence of its 16S rRNA, it was suggested that strain SRKP2 was similar to Brevibacterium casei. PHAs were synthesized from a medium containing dairy waste, yeast extract and sea water. The synthesized PHAs were characterized by FT-IR as Polyhydroxybutyrate (PHB). Response surface methodology was applied to optimize the production of PHB. From the optimized medium the yield of PHB was found to be 2.940 g/L. Here we report the direct use of dairy waste and sea water as potential sources for the production of PHB. Produced PHB was used to synthesize nanoparticles using solvent displacement technique.     

Construction of new cross-linked supramolecular polymer with FRET phenomenon based on oligo(p-phenylenevinylene)-linked pillar[5]arene dimer

Cross-linked supramolecular polymers generally show distinct mechanical properties with intriguing functions, which have become one of the hot research topics in recent years. However, the cross-linked supramolecular polymers functionalised with fluorescence resonance energy transfer (FRET) properties have been rarely reported yet. Herein, a new cross-linked supramolecular polymer equipped with efficient FRET property was constructed successfully. The oligo(p-phenylenevinylene)-linked pillar[5]arene dimer (PA-OPV) functioned as a host and energy donor, while four pentanenitrile groups coupled porphyrin (CN-Por) acted as guest with energy acceptor. The supramolecular polymerisation and FRET properties were investigated by using NMR, viscosity, Fluorescence, UV–vis and SEM.     

Hydrogen‐Bonding Induced Cooperative Effect on the Energy Transfer in Helical Polynorbornenes Appended with Porphyrin‐Containing Amidic Alanine Linkers

Polynorbornenes appended with porphyrins containing a range of different linkers are synthesized. The use of bisamidic chiral alanine linkers between the pending porphyrins and the polymeric backbone has been shown to bring the adjacent porphyrin chromophores to more suitable orientation for exciton coupling owing to hydrogen bonding between the adjacent linkers. The hydrogen bonding between the adjacent pendants in these polymers may induce a cooperative effect and therefore render single‐handed helical structures for these polymers. Such a cooperative effect is reflected in the enhancement of FRET efficiencies between zinc–porphyrin and free base porphyrin in random copolymers.     

Non-isothermal kinetic applied to thermal decomposition of commercial alkyd varnish

Summary PHB polyester poly(3-hydroxybutyrate) is an interesting biodegradable polymer and intensively investigated as cast and sheet films with applications in food industry or in medicine. The films obtained are typically brittle and many scientists have attempted to reduce this brittleness by blending with other polymers. PHB from Usina da Pedra was blended with PEG poly(ethyleneglycol) 300 resulting in blend 1 and blend 2. The two mixtures were melted at 200 and quenched at 0&deg;C. TG curves showed that the thermal stability of the blends and the PHB are identical. For these blends the crystallization temperature decreased compared to the pure PHB, which is probably due to the lower nucleation density.     

Pre-Polymerization Enables Controllable Synthesis of Nanosheet-Based Porphyrin Polymers towards High-Performance Li-Ion Batteries

The precise regulation of nucleation growth and assembly of polymers is still an intriguing goal but an enormous challenge. In this study, we proposed a pre-polymerization strategy to regulate the assembly and growth of polymers by facilely controlling the concentration of polymerization initiator, and thus obtained two kinds of different nanosheet-based porphyrin polymer materials using tetrakis-5,10,15,20-(4-aminophenyl) porphyrin (TAPP) as the precursor. Notably, due to the π–π stacking and doping of TAPP during the preparation process, the obtained PTAPP-nanocube material exhibits a high intrinsic bulk conductivity reaching 1.49×10⁻⁴ S m⁻¹. Profiting from the large π-conjugated structure of porphyrin units, closely stacked layer structure and excellent conductivity, the resultant porphyrin polymers, as electrode materials for lithium ion batteries, deliver high specific capacity (≈650 mAh g⁻¹ at the current density of 100 mA g⁻¹), excellent rate performance and long-cycle stability, which are among the best reports of porphyrin polymer-based electrode materials for lithium-ion batteries, to the best of our knowledge. Therefore, such a pre-polymerization approach would provide a new insight for the controllable synthesis of polymers towards custom-made architecture and function.     

Synthesis and characterization of porphyrin‐based D‐π‐A conjugated polymers for polymer solar cells

Two novel porphyrin‐based D‐A conjugated copolymers, PFTTQP and PBDTTTQP , consisting of accepting quinoxalino[2,3‐b′]porphyrin unit and donating fluorene or benzo[1,2‐b:4,5‐b′]dithiophene unit, were synthesized, respectively via a Pd‐catalyzed Stille‐coupling method. The quinoxalino[2,3‐b′]porphyrin, an edge‐fused porphyrin monomer, was used as a building block of D‐A copolymers, rather than the simple porphyrin unit in conventional porphyrin‐based photovoltaic polymers reported in literature, to enhance the coplanarity and to extend the π‐conjugated system of polymer main chains, and consequently to facilitate the intramolecular charge transfer (ICT). The thermal stability, optical, and electrochemical properties as well as the photovoltaic characteristics of the two polymers were systematically investigated. Both the polymers showed high hole mobility, reaching 4.3 × 10^?4 cm² V^?1 s^?1 for PFTTQP and 2.0 × 10^?4 cm² V^?1 s^?1 for PBDTTTQP . Polymer solar cells (PSCs) made from PFTTQP and PBDTTTQP demonstrated power conversion efficiencies (PCEs) of 2.39% and 1.53%, both of which are among the highest PCE values in the PSCs based on porphyrin‐based conjugated polymers. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013