The morphologies of triblock copolymer/homopolymer blend films confined between two neutral hard walls were studied via MC simulations on a simple cubic lattice. For ABA/A and ABA/B blend films, the effects of φh (the volume fraction of the homopolymer) and Mh/Mb (the ratio of the molecular mass of the homopolymer to that of the corresponding blocks) on the morphologies were investigated in detail. For both ABA/A and ABA/B blend films, a higher φh or Mh/Mb would result in stronger macrophase separation between the triblock copolymer and homopolymer. For ABA/C blend films, Mh/Mb hardly influences the morphologies of homopolymer domains regardless of whether the homopolymer C is more compatible with block A or with block B. Compared to AB/A and AB/C blend films, the morphologies of ABA/A (or ABA/B) and ABA/C blend films are much more irregular. The simulated results in this work show good consistency with experiments and other simulations.
The morphologies of triblock copolymer/homopolymer blend films, ABA/A and ABA/B,confined between two neutral hard walls were studied via Monte Carlo (MC) simulation on a simple cubic lattice. The effects of ψh (the volume fraction of homopolymer) and Mn/Mb (the molecular weight of homopolymer in relation to that of the corresponding blocks in the copolymer) on the morphologies were investigated in detail. 相似文献
We propose the quantitative mean-field theory of mechanical unfolding of a globule formed by long flexible homopolymer chain collapsed in poor solvent and subjected to an extensional force We show that with an increase in the applied force the globule unfolds as a whole without formation of an intermediate state. The value of the threshold force and the corresponding jump in the distance between chain ends increase with a deterioration of the solvent quality and / or with an increase in the degree of polymerization. This way of globule unfolding is compared with that in the D-ensemble, when the distance between chain ends is imposed. 相似文献
The reaction cellulase (EC 3.2.1.4)—sodium carboxymethylcellulose (Na-CMC) with different degrees of polymerization (n=140, 640 and 900) was investigated by the use of a modifiedMichaelis-Menten equation, valid for enzymatic hydrolysis of linear homopolymers. TheMichaelis-Menten constant [Km (M)=6.31·10–2mol/dm3] and the reaction rate constant (k+2=4.07·10–6s–1), which correspond to the enzymatic hydrolysis of a single bond in the homopolymer substrates are determined. The free energy (
=101 kJ/mol), which corresponds to the degradation and formation of a single bond in the enzyme—polymer substrate is also estimated. This energy expressed in electronvolt units is
=1.39 eV. The ratio between the effective cross section of the reactive substrate bond and the active enzyme center is =1.22.
Kinetik der enzymkatalysierten Hydrolyse von Natriumcarboxymethylcellulose mit verschiedenem Polymerisationsgrad durch Cellulase
Zusammenfassung Die modifizierte Gleichung nachMichaelis-Menten wird bei der durch Cellulase (EC 3.2.1.4) katalysierten hydrolytischen Spaltung von Natriumcarboxy-methylcellulose (Na-CMC) verschiedenen Polymerisationsgrades (n=140, 640 und 900) angewandt. Es wurde dieMichaelis-Menten-Konstante [Km (M)=6.31·10–2mol/dm3] und die Reaktionsgeschwindigkeitskonstante (k+2=4.07·10–6s–1), die der enzymatischen Hydrolyse einer Einfachbindung im homopolymeren Substrat entspricht, berechnet. Die freie Energie (
=101 kJ/mol), die dem Abbau und der Bildung einer Einfachbindung im Enzym—Polymer-Substrat entspricht, wurde bestimmt. Diese Energie — ausgedrückt in Elektronvolt-Einheiten — beträgt
=1.39 eV. Das Verhältnis zwischen den effektiven Querschnitten der reaktiven Substratbindung (S) und des aktiven Enzym-Zentrums (E) beträgt =1.22.
Recently, a window of molar mass has been identified where poly(tetrafluoroethylene) (PTFE) homopolymer can be processed from the melt, but at the same time has good mechanical properties in the solid state, so called HD-PTFE®. This research evaluates the use of conventional melt-compounding with a co-rotating twin-screw to introduce a variety of fillers in this material. It was found that melt-compounding is indeed an efficient way to achieve a filler distribution of excellent homogeneity in HD-PTFE®. 相似文献
A simple approach for one‐pot, one‐step binary mixed homopolymer brush synthesis was devised by combining nitroxide‐mediated radical polymerization of styrene and living cationic ring‐opening polymerization of 2‐phenyl‐2‐oxazoline. Surface characterization techniques such as ATR‐FTIR, ellipsometry, XPS, and contact angle measurements were performed in this research. The mixed homopolymer brush exhibited reversible surface property changes when subjected to different solvents. 相似文献
In this study, a novel library of thermoresponsive homopolymers based on poly (ethylene glycol) (EG) (m)ethyl ether methacrylate monomers is presented. Twenty-seven EG based homopolymers were synthesized and three parameters, the molar mass (MM), the number of the ethylene glycol groups in the monomer, and the chemistry of the functional side group were varied to investigate how these affect their thermoresponsive behavior. The targeted MMs of these polymers are varied from 2560, 5000, 8200 to 12,000 g mol−1. Seven PEG-based monomers were investigated: ethylene glycol methyl ether methacrylate (MEGMA), ethylene glycol ethyl ether methacrylate (EEGMA), di(ethylene glycol) methyl ether methacrylate (DEGMA), tri(ethylene glycol) methyl ether methacrylate (TEGMA), tri(ethylene glycol) ethyl ether methacrylate (TEGEMA), penta(ethylene glycol) methyl ether methacrylate (PEGMA), nona(ethylene glycol) methyl ether methacrylate (NEGMA). Homopolymers of 2-(dimethylamino) ethyl methacrylate (DMAEMA) were also synthesized for comparison. The cloud points of these homopolymers were tested in different solvents and it was observed that it decreases as the number of EG group was decreased or the MM increased. Interestingly, the end functional group (methoxy or ethoxy) of the side group has an effect as well and is even more dominant than the number of EG groups. 相似文献
Supramolecular copolymers can not only enrich the diversity of the polymer backbone but also exhibit certain special and improved properties compared with supramolecular homopolymers. However, the synthesis procedure of supramolecular copolymers is relatively complicated and time‐consuming. Herein, a simple transformation from an AB2‐based supramolecular hyperbranched homopolymer to an AB2+CD2‐based supramolecular hyperbranched alternating copolymer by the “competitive self‐sorting” strategy is reported. After adding CD2 monomer, which bears a competitive neutral guest moiety ( TAPN ) and two receptive benzo‐21‐crown‐7 host moieties ( B21C7 ), to the as‐prepared AB2‐type supramolecular hyperbranched homopolymer constructed by the self‐assembly of dialkylammonium salt ( DAAS , A group)‐functionalized pillar[5]arene ( MeP5 , B groups) monomers, the initial homopolymer structure is disrupted and then reassemble into a new supramolecular hyperbranched alternating copolymer based on the competitive self‐sorting interaction between MeP5 ‐ TAPN and B21C7 ‐ DAAS . This study supplies a convenient approach to directly transform supramolecular homopolymers into supramolecular copolymers.