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1.
J Exp Biol ; 227(1)2024 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-38018408

RESUMO

The most effective way to avoid intense inter- and intra-specific competition at the dung source, and to increase the distance to the other competitors, is to follow a single straight bearing. While ball-rolling dung beetles manage to roll their dung balls along nearly perfect straight paths when traversing flat terrain, the paths that they take when traversing more complex (natural) terrain are not well understood. In this study, we investigate the effect of complex surface topographies on the ball-rolling ability of Kheper lamarcki. Our results reveal that ball-rolling trajectories are strongly influenced by the characteristic scale of the surface structure. Surfaces with an increasing similarity between the average distance of elevations and the ball radius cause progressively more difficulties during ball transportation. The most important factor causing difficulties in ball transportation appears to be the slope of the substrate. Our results show that, on surfaces with a slope of 7.5 deg, more than 60% of the dung beetles lose control of their ball. Although dung beetles still successfully roll their dung ball against the slope on such inclinations, their ability to roll the dung ball sideways diminishes. However, dung beetles do not seem to adapt their path on inclines such that they roll their ball in the direction against the slope. We conclude that dung beetles strive for a straight trajectory away from the dung pile, and that their actual path is the result of adaptations to particular surface topographies.


Assuntos
Comportamento Animal , Besouros , Animais , Sinais (Psicologia) , Fezes , Extremidade Superior
2.
J Theor Biol ; 520: 110659, 2021 07 07.
Artigo em Inglês | MEDLINE | ID: mdl-33662373

RESUMO

The majority of biologically inspired dynamic problems are essentially defined by the complexity of the contact surface where such motion takes place. From a statistical point of view, such a surface in many biological problems is typically a combination of a universal scale invariant (fractal) component and a well-defined component having a characteristic scale. If the biological object, here a dung ball, or its parts have a size comparable to the dimensions of the surface peculiarities, one can expect a strong influence on the motion. To avoid competition for the same food resource, some dung-feeding insect species form a dung ball and roll it away from the dung pile. In order to quickly escape competition, dung beetles seem to strictly follow an initial bearing. On flat terrain, they manage to roll a dung ball along a nearly perfect straight path. However, on a more realistic terrain, which normally includes both components mentioned above, the motion is more complex. In this study, we numerically model the ball transportation on terrain with different scales of surface profile. A strong correlation is observed between effective ball transportation (time, distance, work) and the ratio of the size of the ball relative to the size of the terrain roughness. Surface irregularities, with a characteristic size comparable to the ball diameter, are negatively correlated to the efficiency of ball transportation. In addition a strong correlation is found between the quasi random noise, numerically simulating the activity of a dung beetle trying to escape from a valley in which it is trapped, and the success in ball transportation.


Assuntos
Besouros , Animais , Comportamento Animal , Meio Ambiente , Fezes , Movimento (Física)
3.
Int J Mol Sci ; 22(22)2021 Nov 12.
Artigo em Inglês | MEDLINE | ID: mdl-34830139

RESUMO

A new polycondensation aromatic rigid-chain polyester macroinitiator was synthesized and used to graft linear poly-2-ethyl-2-oxazoline as well as poly-2-isopropyl-2-oxazoline by cationic polymerization. The prepared copolymers and the macroinitiator were characterized by NMR, GPC, AFM, turbidimetry, static, and dynamic light scattering. The molar masses of the polyester main chain and the grafted copolymers with poly-2-ethyl-2-oxazoline and poly-2-isopropyl-2-oxazoline side chains were 26,500, 208,000, and 67,900, respectively. The molar masses of the side chains of poly-2-ethyl-2-oxazoline and poly-2-isopropyl-2-oxazoline and their grafting densities were 7400 and 3400 and 0.53 and 0.27, respectively. In chloroform, the copolymers conformation can be considered as a cylinder wormlike chain, the diameter of which depends on the side chain length. In water at low temperatures, the macromolecules of the poly-2-ethyl-2-oxazoline copolymer assume a wormlike conformation because their backbones are well shielded by side chains, whereas the copolymer with short side chains and low grafting density strongly aggregates, which was visualized by AFM. The phase separation temperatures of the copolymers were lower than those of linear analogs of the side chains and decreased with the concentration for both samples. The LCST were estimated to be around 45 °C for the poly-2-ethyl-2-oxazoline graft copolymer, and below 20 °C for the poly-2-isopropyl-2-oxazoline graft copolymer.


Assuntos
Poliaminas/química , Poliésteres/química , Polímeros/química , Temperatura , Algoritmos , Clorofórmio/química , Cinética , Microscopia de Força Atômica , Modelos Químicos , Conformação Molecular , Estrutura Molecular , Peso Molecular , Polímeros/síntese química , Espectroscopia de Prótons por Ressonância Magnética , Temperatura de Transição , Água/química
4.
Bull Math Biol ; 82(7): 93, 2020 07 14.
Artigo em Inglês | MEDLINE | ID: mdl-32661566

RESUMO

In this paper, we introduce general idea of trajectories attraction in phase space, which is very common phenomenon for the processes in the Nature. We start from a rather general biological example of natural selection, where adaptation to the environmental conditions can be described as attraction of some population distribution in the phenotype space to a center of ecological niche. The niche is mathematically represented as the "survival coefficient" which in turn can be linked to a kind of energy potential. This link between biological and physical approaches may be very useful for solution of a wide range of biological problems. In particular, we discuss an evolution in complex potential with a lot of valleys in a multi-dimensional space accompanied by the so-called large river effect, which corresponds to an extremely slow evolution of some, normally close to final, stages of the adaptation. This effect is related to the practically important states of the "frozen kinetics" which accompanies extremely wide spectrum of phenomena and allows understanding different physical and biological processes.


Assuntos
Modelos Biológicos , Seleção Genética , Adaptação Fisiológica , Adesividade , Animais , Formigas/fisiologia , Evolução Biológica , Ecossistema , Insetos/fisiologia , Cinética , Conceitos Matemáticos , Dinâmica não Linear , Dispersão de Sementes/fisiologia , Biologia de Sistemas
5.
Artigo em Inglês | MEDLINE | ID: mdl-29368167

RESUMO

The high importance of resilin in invertebrate biomechanics is widely known. It is generally assumed to be an almost perfect elastomer in different tissues. Whereas mechanical properties of resilin were previously determined mainly in tension, here we aimed at studying its mechanical properties in compression. Microindentation of resilin from the wing hinge of Locusta migratoria revealed the clear viscoelastic response of resilin: about a quarter of the mechanical response was assigned to a viscous component in our experiments. Mechanical properties were characterized using a generalized Maxwell model with two characteristic time constants, poroelasticity theory, and alternatively using a 1D model with just one characteristic time constant. Slow viscous responses with 1.7 and 16 s characteristic times were observed during indentation. These results demonstrate that the locust flight system is adapted to both fast and slow mechanical processes. The fast highly elastic process is related to the flight function and the slow viscoelastic process may be related to the wing folding.


Assuntos
Proteínas de Insetos/metabolismo , Animais , Elasticidade , Ligamentos/metabolismo , Locusta migratoria , Modelos Biológicos , Estresse Mecânico , Viscosidade , Asas de Animais/metabolismo
6.
J Theor Biol ; 430: 1-8, 2017 10 07.
Artigo em Inglês | MEDLINE | ID: mdl-28687224

RESUMO

Certain arachnids exhibit complex coatings of their exoskeleton, consisting of globular structures with complex surface features. This, so-called, cerotegument is formed by a multi-component colloidal secretion that self-assembles and cures on the body surface, and leads to high water repellency. Previous ultrastructural studies revealed the involvement of different glandular cells that contribute different components to the secretion mixture, but the overall process of self-assembly into the complex regular structures observed remained highly unclear. Here we study this process from a theoretical point of view, starting from the so-called Tammes-problem. We show that slight changes of simple parameters lead to a variety of morphologies that are highly similar to the ones observed in the species specific cerotegument structures of whip-spiders. These results are not only important for our understanding of the formation of globular hierarchical structures in nature, but also for the fabrication of novel surface coatings by colloidal lithography.


Assuntos
Exoesqueleto/química , Aracnídeos/anatomia & histologia , Coloides/metabolismo , Animais , Interações Hidrofóbicas e Hidrofílicas , Modelos Teóricos , Especificidade da Espécie , Aranhas/anatomia & histologia , Propriedades de Superfície , Molhabilidade
7.
J Theor Biol ; 384: 140-6, 2015 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-26341386

RESUMO

Genital diversification in animals is an interesting evolutionary phenomenon. Sexual selection is the main driving force behind the diversification. However, evolutionary mechanisms that have established and maintained variations in genitalia shape parameters observed in related species are not well understood. Here, for the first time, we used numerical simulations to test the hypothesis that variations in female spermathecal duct shapes among related beetle species mechanically interfere with penile propulsion in varying ways. Our numerical simulations showed that high curvature of the spiraled spermathecal ducts of the female have effects with a threshold-based interaction on male penile insertion. The relative size of spirals observed in the beetle, Cassida rubiginosa, studied here is not small enough to interfere with penile propulsion. But the model revealed that propulsion is impeded by the presence of reverse turns in spermathecal ducts. This type of morphology leads to an increase in the velocity of the propulsion but also to an increase in the propulsion energy cost for males. Our results showed that quantitative differences in spermathecal duct shape can mediate qualitative differences in penile motion. This explains, in part, the mechanism behind origin and maintenance of genital divergence among closely related species in general.


Assuntos
Besouros/fisiologia , Copulação/fisiologia , Genitália Feminina/fisiologia , Modelos Biológicos , Pênis/fisiologia , Animais , Biometria/métodos , Besouros/anatomia & histologia , Feminino , Genitália Feminina/anatomia & histologia , Masculino , Cauda do Espermatozoide/fisiologia
8.
Support Care Cancer ; 23(10): 2917-23, 2015 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-25724407

RESUMO

PURPOSE: This study aims to compare the efficacy and safety of oral palonosetron with intravenous (IV) palonosetron for the prevention of cisplatin-related chemotherapy-induced nausea and vomiting (CINV). METHODS: A multinational, randomized, double-blind study enrolling adult chemotherapy-naive patients with malignant solid tumors scheduled to receive cisplatin-based highly emetogenic chemotherapy (HEC). Patients received oral palonosetron (0.50 mg) or IV palonosetron (0.25 mg), each with oral dexamethasone. The primary objective was to demonstrate non-inferiority in terms of patients with a complete response (CR, no emesis/no rescue medication) within the acute phase (0-24 h after chemotherapy administration). RESULTS: Of the 743 patients randomized, 739 received study medications and 738 were included in the full analysis set. The CR rate in the acute phase was high for both groups (oral 89.4 %; IV 86.2 %). As this difference in proportions (stratum-adjusted Cochran-Mantel-Haenszel method) was 3.21 % (99 % confidence interval (CI) -2.74 to 9.17 %), non-inferiority was demonstrated (since the lower limit of the 99 % CI was closer to zero than the predefined margin of 15 %). Treatment-emergent adverse events (TEAEs) related to the study drug were rare (oral 3.2 %; IV 6.5 %). No TEAEs related to study drug leading to discontinuation were reported. CONCLUSION: Non-inferiority of oral versus IV palonosetron was demonstrated. The CR rate in the acute phase was >86 % in both patient groups. The safety profiles were comparable.


Assuntos
Cisplatino/efeitos adversos , Dexametasona/uso terapêutico , Isoquinolinas/uso terapêutico , Náusea/prevenção & controle , Neoplasias/complicações , Quinuclidinas/uso terapêutico , Vômito/prevenção & controle , Administração Intravenosa , Administração Oral , Antieméticos/uso terapêutico , Cisplatino/farmacologia , Dexametasona/administração & dosagem , Método Duplo-Cego , Feminino , Humanos , Isoquinolinas/administração & dosagem , Isoquinolinas/farmacologia , Masculino , Pessoa de Meia-Idade , Náusea/induzido quimicamente , Neoplasias/tratamento farmacológico , Palonossetrom , Quinuclidinas/administração & dosagem , Quinuclidinas/farmacologia , Vômito/induzido quimicamente
9.
Ecol Evol ; 14(7): e11715, 2024 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-39045500

RESUMO

We explore the use of movable automata in numerical modelling of male competition for territory. We used territorial dragonflies as our biological inspiration for the model, assuming two types of competing males: (a) faster and larger males that adopt a face-off strategy and repulse other males; (b) slower and smaller males that adopt a non-aggressive strategy. The faster and larger males have higher noise intensity, leading to faster motion and longer conservation of motion direction. The velocity distributions resemble the Maxwell distributions of velocity, expected in Brownian dynamics, with two probable velocities and distribution widths for the two animal subpopulations. The fast animals' trajectories move between visually fixed density folds of the slower animal subpopulation. A correlation is found between individual velocity and individual area distribution, with smaller animals concentrated in a region of small velocities and areas. Attraction between animals results in a modification of the system behaviour, with larger animals spending more time being surrounded by smaller animals and being slowed down by their interaction with the surroundings. Overall, the study provides insights into the dynamics of animal competition for territory and the impact of attraction between animals.

10.
Phys Rev Lett ; 111(10): 104301, 2013 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-25166671

RESUMO

Nature has successfully evolved the mushroom-shaped contact geometry in many organisms in order to solve the attachment problem. We studied the detachment process of individual bioinspired artificial mushroom-shaped adhesive microstructures (MSAMSs) resolving the failure dynamics at high spatiotemporal resolution. The experimental data provide strong evidence for a homogeneous stress distribution in MSAMS, which was recently proposed. Our results allow us to explain the advantage of such contact geometry and provide a suggestion for the widely observed mushroom-shaped contact geometry.


Assuntos
Adesivos/química , Materiais Biomiméticos/química , Adesividade , Fenômenos Biomecânicos , Teste de Materiais/instrumentação , Teste de Materiais/métodos , Propriedades de Superfície , Gravação em Vídeo
11.
Cell Mol Neurobiol ; 33(1): 1-4, 2013 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-22872321

RESUMO

Some of the excitatory effects of norepinephrine on central neurons are mediated by alpha-1 (α1) adrenoceptors. These receptors are coupled to the Gq family of G proteins, and hence stimulate hydrolysis of the membrane phospholipid phosphatidylinositol-4,5-bisphosphate. Other receptors of this type can excite neurons by inhibiting the subthreshold voltage-gated potassium M-current. We tested this possibility using rat sympathetic neurons transformed to express α1a receptors. The α1 agonist phenylephrine strongly inhibited the M-current recorded under voltage-clamp by 72 ± 11 % (n = 4) and in an unclamped neuron dramatically increased the number of action potentials produced by a 2 s depolarizing current step from 2 to 40, without effect on control neurons devoid of α1 receptors. We suggest that this might be a potential cause of the increased excitability produced by norepinephrine in some central neurons.


Assuntos
Norepinefrina/fisiologia , Bloqueadores dos Canais de Potássio/farmacologia , Canais de Potássio de Abertura Dependente da Tensão da Membrana/antagonistas & inibidores , Canais de Potássio de Abertura Dependente da Tensão da Membrana/fisiologia , Receptores Adrenérgicos alfa 1/fisiologia , Agonistas de Receptores Adrenérgicos alfa 1/farmacologia , Animais , Células Cultivadas , Gânglios Simpáticos/efeitos dos fármacos , Gânglios Simpáticos/fisiologia , Potenciais da Membrana/efeitos dos fármacos , Potenciais da Membrana/fisiologia , Inibição Neural/efeitos dos fármacos , Inibição Neural/fisiologia , Fenilefrina/farmacologia , Ratos
12.
Polymers (Basel) ; 15(7)2023 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-37050255

RESUMO

The thermo- and pH-responsive polymer brushes based on methoxy[oligo(propyleneglycol)8-block-oligo(ethyleneglycol)8]methacrylate with different concentrations of N-[3-(dimethylamino)propyl]methacrylamide (from 0% to 20%) were synthesized via RAFT polymerization. The "grafting-through" approach was used to prepare the low-molar-mass dispersion samples (Mw/Mn ≈ 1.3). Molar masses and hydrodynamic characteristics were obtained using static and dynamic light scattering and viscometry. The solvents used were acetonitrile, DMFA, and water. The molar masses of the prepared samples ranged from 40,000 to 60,000 g·mol-1. The macromolecules of these polymer brushes were modeled using a prolate revolution ellipsoid or a cylinder with spherical ends. In water, micelle-like aggregates were formed. Critical micelle concentrations decreased with the content of N-[3-(dimethylamino)propyl]methacrylamide. Molecular brushes demonstrated thermo- and pH-responsiveness in water-salt solutions. It was shown that at a given molecular mass and at close pH values, the increase in the number of N-[3-(dimethylamino)propyl]methacrylamide units led to an increase in phase separation temperatures.

13.
Beilstein J Nanotechnol ; 14: 603-615, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37228744

RESUMO

Suspension feeding via setae collecting particles is common within Crustacea. Even though the mechanisms behind it and the structures themselves have been studied for decades, the interplay between the different setae types and the parameters contributing to their particle collecting capacities remain partly enigmatic. Here, we provide a numerical modeling approach to understand the relationship among the mechanical property gradients, the mechanical behavior and the adhesion of setae, and the feeding efficiency of the system. In this context, we set-up a simple dynamic numerical model that takes all of these parameters into account and describes the interaction with food particles and their delivery into the mouth opening. By altering the parameters, it was unraveled that the system performs best when the long and short setae have different mechanical properties and different degrees of adhesion since the long setae generate the feeding current and the short ones establish the contact with the particle. This protocol can be applied to any system in the future as the parameters (i.e., properties and arrangement of particles and setae) can be easily altered. This will shed light on the biomechanical adaptations of these structures to suspension feeding and provide inspiration for biomimetics in the field of filtration technologies.

14.
Polymers (Basel) ; 15(13)2023 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-37447567

RESUMO

For the first time, a study of the influence of the molecular weight of the thermoplastic partially crystalline polyimide R-BAPB on the thermophysical and mechanical properties of carbon plastics was presented. The molecular weight of polyimide was determined using the method of light scattering and the study of the intrinsic viscosity of polyamic acid solutions. To obtain CFRPs, the uniform distribution of polyimide powder on continuous carbon fibers via electrostatic spraying and further hot calendering and pressing were applied. The study of the structure of the obtained carbon plastics via scanning electron microscopy has shown that the growth of the molecular weight of polyimide prevents the impregnation of carbon fiber with the introduced polyimide. Moreover, an increase in the molecular weight of polyimide leads to a rise in glass transition and thermal decomposition temperatures up to 590 °C, while the degree of crystallinity of CFRP falls. Nonetheless, raising the molecular weight from 22,000 to 70,000 g/mol of a binder polymer improves the interlayer fracture toughness G1C by more than five times.

15.
J Funct Biomater ; 14(7)2023 Jun 29.
Artigo em Inglês | MEDLINE | ID: mdl-37504843

RESUMO

Platinum nanoparticles (nPts) have neuroprotective/antioxidant properties, but the mechanisms of their action in cerebrovascular disease remain unclear. We investigated the brain bioavailability of nPts and their effects on brain damage, cerebral blood flow (CBF), and development of brain and systemic oxidative stress (OS) in a model of cerebral ischemia (hemorrhage + temporary bilateral common carotid artery occlusion, tBCAO) in rats. The nPts (0.04 g/L, 3 ± 1 nm diameter) were administered to rats (N = 19) intraperitoneally at the start of blood reperfusion. Measurement of CBF via laser Doppler flowmetry revealed that the nPts caused a rapid attenuation of postischemic hypoperfusion. The nPts attenuated the apoptosis of hippocampal neurons, the decrease in reduced aminothiols level in plasma, and the glutathione redox status in the brain, which were induced by tBCAO. The content of Pt in the brain was extremely low (≤1 ng/g). Thus, nPts, despite the extremely low brain bioavailability, can attenuate the development of brain OS, CBF dysregulation, and neuronal apoptosis. This may indicate that the neuroprotective effects of nPts are due to indirect mechanisms rather than direct activity in the brain tissue. Research on such mechanisms may offer a promising trend in the treatment of acute disorders of CBF.

16.
Polymers (Basel) ; 14(23)2022 Nov 29.
Artigo em Inglês | MEDLINE | ID: mdl-36501588

RESUMO

The amphiphilic block copolymer poly(N-isopropylacrylamide)-Ge(C6F5)2-poly(2,2,3,3-tetrafluoropropyl methacrylate) was prepared by the reaction of chain transfer to bis-(pentafluorophenyl)germane during the polymerization of N-isopropylacrylamide and the subsequent postpolymerization of isolated functional polymers in 2,2,3,3-tetrafluoropropyl methacrylate. The conversion of the block copolymer was 68% and the molecular weight of the sample was 490,000 g/mol. The colloidal chemical properties of Langmuir monolayers and Langmuir-Blodgett films of synthesized block copolymer have been studied. For comparison, a functional polymer, namely, poly-N-isopropylacrylamide with terminal -Ge(C6F5)2H group, was synthesized and studied. The concentrations of spreading solutions were selected and the effect of subphase acidity on the formation of monolayers of macromolecules of the block copolymer was studied. It was found that regardless of the acidity of the subphase, high pressure of fracture of films are characteristic of monolayers of collapse pressures πmax = (48-61) mN/m. The morphology of the Langmuir-Blodgett films of functional polymer exhibit isolated elongated micelles with high densities in the form of "octopus" on the periphery of which there are terminal hydrophobic groups. For the Langmuir-Blodgett film of block copolymer, a comb-like structure is observed with characteristic protrusions.

17.
Polymers (Basel) ; 14(2)2022 Jan 11.
Artigo em Inglês | MEDLINE | ID: mdl-35054689

RESUMO

Thermo- and pH-responsive poly(N-[3-(diethylamino)propyl]methacrylamide)s were synthesized by free radical polymerization and RAFT polymerization. The molar masses of the samples were 33,000-35,000 g∙mol-1. Investigations of the dilute solutions showed that the prepared samples were flexible chain polymers. The behavior of the synthesized polymers in the buffer solutions was analyzed by turbidity and light scattering at a pH range of 7-13 and a concentration range of 0.0002-0.008 g·cm-3. When the concentrated solutions were at a low temperature, there were macromolecules and aggregates, which were formed due to the interaction of hydrophobic units. For the investigated samples, the lower critical solution temperatures were equal. The phase separation temperatures decreased as pH increased. The influence of polydispersity index on the characteristics of the samples in the solutions was analyzed. The radii of molecules of poly(N-[3-(diethylamino)propyl]methacrylamide) obtained by RAFT polymerization at this temperature at the onset and end of the phase separation interval were lower than ones for samples synthesized by conventional free radical polymerization.

18.
Polymers (Basel) ; 14(24)2022 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-36559721

RESUMO

A polycondensation aromatic polyester with an oxygen spacer was synthesized and used as a macroinitiator for the grafting of linear poly(2-isopropyl-2-oxazoline) (PiPrOx) by the cationic polymerization method. The length of the thermosensitive side chains was varied by the initiator:monomer ratio. Using methods of molecular hydrodynamics, light scattering and turbidimetry, the copolymers were studied in organic solvents and in water. The molecular characteristics of the main chain and graft copolymers, the polymerization degree of side chains and their grafting density have been determined. The equilibrium rigidity of the macroinitiator and the conformations of grafted macromolecules were evaluated. In selective solvents, they take on a star-like conformation or aggregate depending on the degree of shielding of the main chain by side chains. The thermoresponsiveness of graft copolymers in aqueous solutions was studied, and their LCST were estimated. The results are compared with data for graft copolymers composed of PiPrOx side chains and flexible or rigid chain backbones of aromatic polyester type.

19.
Polymers (Basel) ; 14(23)2022 Nov 24.
Artigo em Inglês | MEDLINE | ID: mdl-36501510

RESUMO

Regular and irregular molecular brushes with polydimethylsiloxane backbone and poly-2-isopropyl-2-oxazoline side chains have been synthesized. Prepared samples differed strongly in the side chain grafting density, namely, in the ratio of the lengths of spacer between the grafting points and the side chains. The hydrodynamic properties and molecular conformation of the synthesized grafted copolymers and their behavior in aqueous solutions on heating were studied by the methods of molecular hydrodynamics and optics. It was found that the regularity and the grafting density do not affect the molecular shape of the studied samples of molecular brushes in the selective solvent. On the contrary, the grafting density is one of the most important factors determining the thermoresponsivity of grafted copolymers. It was shown that in analyzing self-organization and LCST values in aqueous solutions of poly-2-isopropyl-2-oxazolines with complex architecture, many factors should be considered. First is the molar fraction of the hydrophobic fragment and the intramolecular density. It was found that molar mass is not a factor that greatly affects the phase transition temperature of poly-2-isopropyl-2-oxazolines solutions at a passage from one molecular architecture to another.

20.
Polymers (Basel) ; 14(24)2022 Dec 19.
Artigo em Inglês | MEDLINE | ID: mdl-36559923

RESUMO

The properties of polymer brushes based on three macromonomers were investigated in aqueous and organic solutions. Methacrylic monomers with different compositions of the oligo(oxyalkylene) substituents and arrangements of the oligo(ethylene glycol) and oligo(propylene glycol) blocks were used for the synthesis of polymers. There were methoxy [oligo(ethylene glycol)10.3-block-oligo(propylene glycol)4.7] methacrylate, methoxy [oligo(propylene glycol)8.3-block-oligo(ethylene glycol)6.6] methacrylate, and methoxy oligo(propylene glycol)4.2 methacrylate. Molecular brushes were investigated by the methods of molecular hydrodynamics and optics in dilute solutions in acetonitrile, chloroform, and water. The peculiarities of behavior of poly[oligo(oxyalkylene) methacrylates] in aqueous solutions and water-toluene systems have been found; in particular, the solubility of the polymers in water and organic solvents, the polymers equilibrium distribution between the phases, and the surface activity in the water-toluene system have been established. The thermo-responsibility in aqueous solutions and values of a critical concentration of micelle formation were shown. Depending on the arrangement of blocks in the side chains of molecular brushes, they are characterized by different intramolecular density.

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