Varying Side Chain Lengths Research Articles

Diagonal Interactions between Glutamate and Arginine Analogs with Varying Side-Chain Lengths in a β-Hairpin

Cross-strand interactions are important for the stability of β-sheet structures. Accordingly, cross-strand diagonal interactions between glutamate and arginine analogs with varying side-chain lengths were studied in a series of β-hairpin peptides. The peptides were analyzed by homonuclear two-dimensional nuclear magnetic resonance methods. The fraction folded population and folding free energy of the peptides were derived from the chemical shift data. The fraction folded population trends could be rationalized using the strand propensity of the constituting residues, which was not the case for the peptides with lysine analogs, highlighting the difference between the arginine analogs and lysine analogs. Double-mutant cycle analysis was used to derive the diagonal ion-pairing interaction energetics. The most stabilizing diagonal cross-strand interaction was between the shortest residues (i.e., Asp2-Agp9), most likely due to the least side-chain conformational penalty for ion-pair formation. The diagonal interaction energetics in this study involving the arginine analogs appears to be consistent with and extend beyond our understanding of diagonal ion-pairing interactions involving lysine analogs. The results should be useful for designing β-strand-containing molecules to affect biological processes such as amyloid formation and protein-protein interactions.

Biobased, Degradable, and Conjugated Poly(Azomethine)s.

Carotenoids are a class of biobased conjugated molecules that bear a resemblance to the substructure of polyacetylene, a well-known conductive but insoluble polymer. Solubility is an important physical attribute for processing materials using different techniques. To impart solubility in polymers, alkyl side chains are often included in the molecular design. While these design strategies are well explored in conjugated systems, they have not been implemented with carotenoids as a building block in polymers. Here, we show a series of carotenoid-based polymers with varying side chain lengths to tune solubility. Using carotenoid and p-phenylenediamine-based monomers, degradable and biobased poly(azomethine)s were synthesized via imine polycondensation. Maximum solubilities corresponding to the varying alkyl chain lengths were quantitatively determined by ultraviolet-visible (UV-vis) absorption spectroscopy. Since carotenoids are biobased with known degradation products, the effect of acidic and artificial sunlight-promoted degradation was systematically investigated using UV-vis spectroscopy, 1H nuclear magnetic resonance (NMR) spectroscopy, infrared (IR) spectroscopy, gel permeation chromatography (GPC), and high-resolution mass spectroscopy (HRMS). Our polymer system was found to have two modes of on-demand degradation, with acid hydrolysis accelerating the rate of polymer degradation and artificial sunlight generating additional degradation products. This work highlights carotenoid monomers as viable candidates in the design of biobased, degradable, and conjugated polymers.

Brain ethanolamine phospholipids, neuropathology and cognition: A comparative post-mortem analysis of structurally specific plasmalogen and phosphatidyl species.

Reduced cognition in the elderly is associated with low levels of plasmalogens and high levels of lipid rafts, amyloid plaques, and neurofibrillary tangles in the temporal cortex. A systematic integrative analysis of key indices of these pathologies to determine their collective and independent contributions to cognition was performed. Levels of four phosphatidylethanolamines (PE) and four ethanolamine plasmalogens (PL) of identical sn-1 carbon length and desaturation (stearic, 18:0) and identical sn-2 fatty acid compositions of varying side chain lengths and degrees of unsaturation (oleic, 18:1; linoleic, 18:2; arachidonic, 20:4; docosahexaenoic, 22:6), flotillin-1 expression and amyloid plaque and neurofibrillary tangle densities were measured in inferior temporal cortex tissue from 100 elderly subjects (Rush University Memory and Aging Project, 88.5 ± 5.8 years old). Subjects were evenly distributed with respect to gender (52/48, F/M) and cognitive status (38/24/38, no cognitive impairment/mild cognitive impairment/Alzheimer’s dementia) proximate to death. Multivariate logistic regression analyses were used to determine the relative and collective associations of the neuropathological indices with cognition. Higher levels of tangles, amyloid, or flotillin and lower levels of PL 18:0/22:6 were significantly associated with lower cognition in the base model (adjusted for age, sex, education). Multivariate analysis revealed that only PL 18:0/22:6 (β = 0.506; p < 0.00001), tangles (−0.307; p < 0.01), and flotillin (−0.2027; p < 0.05) were independently associated with reduced cognition. PL 18:0/22:6 and PE 18:0/22:6 levels were independently associated with cognition in the presence of tangles, amyloid, and flotillin, but only PL 18:0/22:6 retained its association with cognition when both PL and PE 18:0/22:6 were included in the model indicating that PE 18:0/22:6 levels were associated with PL 18:0/22:6, not cognition. Only high brain levels of PL 18:0/22:6 (>mean+1SD) was predictive of normal cognition (coef = 1.67, p < 0.05) and non-demented state (coef = −2.73, p < 0.001), whereas low levels of PL 18:0/22:6 and high levels of tangles or flotillin were predictive of dementia. The association of high brain polyunsaturated (PUFA)-PL levels with better cognition was independent of amyloid plaque, neurofibrillary tangle, PE, and flotillin-1 expression. Maintenance or augmentation of brain docosahexaenoic (DHA)-PL levels warrants further investigation as a target for preventing cognitive decline or improving cognition in the elderly, respectively.

Self-healing antifouling polymer brushes: Effects of degree of fluorination

Heavily fluorinated polymeric coatings are used by industry in the prevention of polymeric fouling. However, due to their potential toxicity and lack of durability, there is an increasing demand for sustainable alternatives. In this research, eleven polymer brushes with varying side chain lengths and degrees of fluorination have been developed, and their antifouling and self-healing performances have been compared. In all cases where damage was inflicted by a pH 3 solution, the coatings – including the non-fluorinated ones – showed full restoration of their contact angle upon placement in an oven at 120 °C, confirming the self-healing ability of this range of coatings. One coating, poly(C10-MAF0), was unharmed by the acidic conditions, hence no self-healing capability could be established. Investigation with four fluorescently labelled polymer solutions and confocal fluorescent microscopy confirmed that all coatings have antifouling properties towards organic polymers. The more heavily fluorinated polymer brushes performed better than the rest, and not the non-fluorinated but rather the singly fluorinated brushes showed the least antifouling capability. Determination of the critical surface tension confirmed this trend: the heavily fluorinated polymer brushes have the lowest critical surface tension, and the singly fluorinated polymer brushes have the highest. A lack of alignment of the side chains of the polymer brushes is the proposed reason for this, explaining the contrast with previously reported monolayer experiments. Finally, we explain why both fluorinated and non-fluorinated brushes display self-healing characteristics.

High Yields of Aromatic Monomers from Acidolytic Oxidation of Kraft Lignin in a Biphasic System

In this work, acidic oxidation in a biphasic water/octanol system was applied to mitigate condensation and increase the yields of high-value aromatic monomers from Kraft lignin, a waste product, and an industrially relevant feedstock. Biphasic depolymerization (BPD) is a one-pot multistep technique in which target molecules are protected from degradation in the reactive aqueous milieu (necessary for the cleavage of β-O-4 bonds as well as the recalcitrant high dissociation energy carbon–carbon moieties) by an in situ transfer of the products into the protective octanol phase. The results have shown overall monomeric yields up to 13 wt % and yields of vanillin up to 7 wt % (FeCl3 as a catalyst and O2 as an oxidant), significantly outperforming the previously reported monophasic and biphasic outcomes for Kraft lignin. In addition to increased yields, BPD also resulted in an expansion of the product pool from few molecules typically reported in the literature to 64 aromatic monomers detected at various concentration levels in the current work. The identified aromatic alcohols, carbonyl compounds, and carboxylic acids incorporating varying side chain lengths show potential as green and sustainable replacements to BTX (benzene, toluene, and xylene) petrochemicals. BPD as a process coupled mild conversion conditions, cheap oxidants, and common homogeneous catalysts with an in situ separation of the products from the reaction mixture to yield excellent results in converting industrial waste and recalcitrant feedstocks into value.

Phase transitions of poly(oligo(ethylene glycol) methyl ether methacrylate)-water systems

The phase diagrams for poly (oligo (ethylene glycol) methyl ether methacrylate) (POEGMA) hydrogels with varying side chain lengths over broad temperature and composition ranges are shown for the first time. It is also shown that the ability of water to crystallize is strictly correlated with the occurrence of a volume phase transition in hydrogels, as both phenomena require the continuous water pathways in the system. A discontinuity in the water phase appears above wp = 0.83 for PMEO2MA and wp = 0.56 for other POEGMAs. In contrast to PMEO2MA, POEGMA hydrogels with longer oligoether chains are characterized by two distinct regimes for the glass transition as a function of polymer content. It was also confirmed that crystallization of the polymer network can be observed for POEGMA networks with suitably long oligoether chain lengths, namely, n ≥ 7. Moreover, the range of the polymer crystalline phase occurrence was found to increase with the length of the oligoether chain.

Synthesis and Characterization of Heterodimers and Fluorescent Nisin Species by Incorporation of Methionine Analogues and Subsequent Click Chemistry.

Noncanonical amino acids form a highly diverse pool of building blocks that can render unique physicochemical properties to peptides and proteins. Here, four methionine analogues with unsaturated and varying side chain lengths were successfully incorporated at four different positions in nisin in Lactococcus lactis through force feeding. This approach allows for residue-specific incorporation of methionine analogues into nisin to expand their structural diversity and alter their activity profiles. Moreover, the insertion of methionine analogues with biorthogonal chemical reactivity, e.g., azidohomoalanine and homopropargylglycine, provides the opportunity for chemical coupling to functional moieties and fluorescent probes as well as for intermolecular coupling of nisin variants. All resulting nisin conjugates retained antimicrobial activity, which substantiates the potential of this method as a tool to further study its localization and mode of action.

Impact of oligoether chain lengths on the relaxation processes in poly(oligo(ethylene glycol) methyl ether methacrylate) networks that are synthesized by radiation-induced crosslinking polymerization

The molecular mobility in poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA) networks with varying side chain lengths (n = 2–19 oxyethylene groups), which are synthetized by radiation-induced crosslinking polymerization, has been investigated by dielectric spectroscopy. A complete relaxation map for these materials with four processes was created for the first time. At higher temperatures, α relaxation corresponding to the dynamic glass transition and α’ relaxation, which was likely correlated with sub-Rouse processes, were found. Below the dynamic glass transition, two Arrhenius-type processes were distinguished: the γ-process, which was assigned to the end (methoxy-) group; and weak β-relaxation, which was dependent on the oligoether chain length and was related to side chain movements. The fragility index for all of the POEGMA networks proves that these are strong glass-forming materials. In the partially crystalline samples with n > 7, the relaxation processes are strongly disturbed by cold crystallization and melting.

Influence of Non-natural Cationic Amino Acids on the Biological Activity Profile of Innate Defense Regulator Peptides.

Non-natural amino acids can be incorporated into synthetic host defense peptides (HDPs) to modulate their susceptibility to proteolytic degradation. However, the impact of non-natural amino acids on the antibiofilm and immunomodulatory activities of synthetic HDPs remains unclear. Using SPOT-synthesized peptide arrays, non-natural cationic amino acids of varying side chain lengths were incorporated into a synthetic HDP, IDR-1018, and the impact of these substitutions on the antibiofilm activity toward methicillin resistant Staphylococcus aureus biofilms was assessed. Multiply-substituted derivatives were designed that incorporated favorable non-natural cationic amino acid moieties throughout IDR-1018. The antibiofilm and immunomodulatory activities of these derivatives were assessed in vitro, revealing that the incorporation of non-natural amino acids modulated (either positively or negatively) these activities of IDR-1018. Furthermore, the tryptic stability of the IDR-1018 derivatives was assessed revealing that proteolytic stability was favored for shorter cationic side chains and was influenced by the primary peptide sequence.

Organic photodiodes from homochiral l-proline derived squaraine compounds with strong circular dichroism.

We suggest and explore a novel route towards organic photodetectors sensitive to the circular polarization state of light. For this, we insert fullerene-blended thin films of homochiral squaraine compounds acting as a highly circular dichroic active layer into conventional bulk hetero-junction photodiodes. Initially, we discuss steady-state characterization of photodiodes with unpolarized light. The homochiral, l-proline derived squaraine compounds are obtained via a chiral pool synthesis in sizable quantities. The aggregation behavior of the two compounds with varying side chain length is complex. They exhibit H-type spectral signatures only in colloidal solution, and both H- and J-type features with large splitting in neat and fullerene-blended thin films. We probe strong excitonic circular dichroism for both aggregate species, showing the most competitive dissymmetry factors up to -0.055 in fullerene-blended thin films. We vary the blend ratio and layer thickness of such active layers in the photodiodes. The device performance is in all cases limited by a low fill factor which is accompanied by a voltage-dependent photocurrent. Current-voltage measurements show light intensity dependent characteristics, which are S-shaped, contrary to our expectations, only for thin active layers independent of the blend ratio. The external quantum efficiency is in some cases extraordinarily high, exceeding 100 percent in the blue spectral range under modest reverse bias voltages for thin, fullerene-rich devices. However, the most promising are the devices with thick, donor-rich layers defined by a spectral overlap of the strongest photocurrent response and the maximum circular dichroism within the green spectral range. Thus, we demonstrate the feasibility of combining photodiode functionality and strong circular dichroism as intrinsic material properties.

Effect of Charged Amino Acid Side Chain Length at Non-Hydrogen Bonded Strand Positions on β-Hairpin Stability

β-Sheets have been implicated in various neurological disorders, and ∼20% of protein residues adopt a sheet conformation. Therefore, studies on the structural origin of sheet stability can provide fundamental knowledge with potential biomedical applications. Oppositely charged amino acids are frequently observed across one another in antiparallel β-sheets. Interestingly, the side chains of natural charged amino acids Asp, Glu, Arg, Lys have different numbers of hydrophobic methylenes linking the backbone to the hydrophilic charged functionalities. To explore the inherent effect of charged amino acid side chain length on antiparallel sheets, the stability of a designed hairpin motif containing charged amino acids with varying side chain lengths at non-hydrogen bonded positions was studied. Peptides with the guest position on the N-terminal strand and the C-terminal strand were investigated by NMR methods. The charged amino acids (Xaa) included negatively charged residues with a carboxylate group (Asp, Glu, Aad in increasing length), positively charged residues with an ammonium group (Dap, Dab, Orn, Lys in increasing length), and positively charged residues with a guanidinium group (Agp, Agb, Arg, Agh in increasing length). The fraction folded and folding free energy for each peptide were derived from the chemical shift deviation data. The stability of the peptides with the charged residues at the N-terminal guest position followed the trends: Asp > Glu > Aad, Dap < Dab < Orn ∼ Lys, and Agb < Arg < Agh < Agp. The stability of the peptides with the charged residues at the C-terminal guest position followed the trends: Asp < Glu < Aad, Dap ∼ Dab < Orn ∼ Lys, and Agb < Arg ∼ Agp < Agh. These trends were rationalized by thermodynamic sheet propensity and cross-strand interactions.

Sequence Position and Side Chain Length Dependence of Charge Pair Interactions in Collagen Triple Helices

In this study, we examine eight ABC heterotrimers whose self-assembly is directed through electrostatic interactions. Oppositely charged pairs of amino acids, with varying side chain length, were assessed for their ability to stabilize a triple helix. Aspartate-lysine was found to result in the most thermally stable helix followed by lysine-glutamate, ornithine-aspartate, and finally ornithine-glutamate. When the sequence position of these charged amino acids was reversed from what is normally observed in nature, triple helix stability and compositional purity were significantly reduced. We examine the effect of salt on triple helix stability and observe that increased salt concentration reduces the thermal stability of heterotrimers by an average of 5 °C, but does not disrupt helix assembly. It was also found that some highly positively charged homotrimers can be stabilized in the presence of phosphate anions.

Helix formation and capping energetics of arginine analogs with varying side chain length

Arginine (Arg) has been used for recognizing negatively charged biological molecules, cell penetration, and oligosaccharide mass signal enhancement. The versatility of Arg has inspired the need to develop Arg analogs and to research the structural effects of incorporating Arg analogs. Accordingly, we investigated the effect of Arg side chain length on helix formation by studying 12 Ala-based peptides containing the Arg analogs (S)-2-amino-6-guanidino-hexanoic acid (Agh), (S)-2-amino-4-guanidinobutyric acid (Agb), and (S)-2-amino-3-guanidinopropionic acid (Agp). Solid phase guanidinylation with orthogonal protection strategies was necessary to synthesize Agb- and Agp-containing peptides using Fmoc-based chemistry. The fraction helix for the peptides was determined by circular dichroism spectroscopy, and used to derive the statistical mechanical parameters and energetics for N-capping, C-capping, and helix propagation (propensity). All four Arg analogs were unfavorable for N-capping. The C-cap parameter followed the trend Agp<Agb<Arg<Agh, showing more favorable C-cap energetics with increasing side chain length. In contrast, helix propensity followed the trend Agp<Agb<Arg>Agh, highlighting the uniqueness of the Arg side chain length in helix formation. Molecular mechanics calculations and a survey on protein structures were consistent with the experimental results. Furthermore, calculations and survey both showed that the g- conformation for the χ1 dihedral was present for the first two residues at the N-terminus of helices, but not favored in the center or C-terminus of helices due to sterics. These results should serve as the foundation for developing Arg-related bioactive compounds and technologies.

Lipophilic derivatives of leu-enkephalinamide: In vitro permeability, stability and in vivo nasal delivery

Leu-enkephalin is an endogenous pain modulating opioid pentapeptide. Its development as a potential pharmaceutic has been hampered by poor membrane permeability and susceptibility to enzymatic degradation. The addition of an unnatural amino acid containing a lipidic side chain at the N-terminus and the modification of the C-terminus to a carboxyamide was performed to enhance the nasal delivery of the peptide. Two lipidic derivatives with varying side chain lengths (C8-Enk-NH2 (1), C12-Enk-NH2 (2)) and their acetylated analogues were successfully synthesised. Caco-2 cell monolayer permeability and Caco-2 cell homogenate stability assays were performed. C8-Enk-NH2 (1) and its acetylated analogue Ac-C8-Enk-NH2 (3) exhibited apparent permeabilities (mean±SD) of 2.51±0.75×10−6cm/s and 1.06±0.62×10−6, respectively. C12-Enk-NH2 (2) exhibited an apparent permeability of 2.43±1.26×10−6cm/s while Ac-C12-Enk-NH2 (4) was not permeable through the Caco-2 monolayers due to its poor solubility. All analogues exhibited improved Caco-2 homogenate stability compared to Leu-Enk-NH2 with t½ values of: C8-Enk-NH2 (1): 31.7min, C12-Enk-NH2 (2): 14.7min, Ac-C8-Enk-NH2 (3): 83min, Ac-C12-Enk-NH2 (4): 27min. However, plasma stability assays revealed that the diastereoisomers of C8-Enk-NH2 (1) did not degrade at the same rate, with the l isomer (t1/2=8.9min) degrading into Leu-enkephalinamide and then des-Tyr-Leu-Enk-NH2, whereas the d isomer was stable (t1/2=120min). In vivo nasal administration of C8-Enk-NH2 to male rats resulted in concentrations of 5.9±1.84×10−2μM in the olfactory bulbs, 1.35±1.01×10−2μM in the brain and 6.53±1.87×10−3μM in the blood 10min after administration.

Linear poly(alkyl ethylene imine) with varying side chain length: synthesis and physical properties

The synthesis of a series of poly(alkyl ethylene imine) (PalkylEI) with varying side chain lengths of 1, 2, 3 and 10 carbon atoms as well as a benzyl side group was performed. A series of polymers was synthesized from a direct reduction reaction of the corresponding poly(2-oxazoline) while another series was prepared by (reductive) alkylation of linear poly(ethylene imine) (PEI). The thermal and solubility properties of the resulting polymers were investigated and compared to the starting poly(2-oxazoline)s in order to study the effects of removing the carbonyl from the polymer structure. 1H NMR spectroscopy revealed quantitative formation of the PalkylEI, i.e. no residual signals of the poly(2-oxazoline) or linear PEI were observed. Thermal investigations revealed that the thermal transitions, melting and glass transition temperatures, significantly decreased after decarboxylation due to an increase in chain flexibility. Furthermore, solubility measurements indicated that the PalkylEIs are more hydrophobic compared to the corresponding poly(2-oxazoline)s, whereby poly(ethyl ethylene imine) revealed pH and temperature responsive solubility behavior in water.

Lower Critical Solution Temperature Behavior of Comb and Graft Shaped Poly[oligo(2-ethyl-2-oxazoline)methacrylate

Comb and graft polymers with lower critical solution temperature (LCST) behavior based on hydrophilic oligo(2-ethyl-2-oxazoline) side chains and a hydrophobic methacrylate backbone were synthesized using the macromonomer method. Well-defined oligo(2-ethyl-2-oxazoline) methacrylate (OEtOxMA) macromonomers were obtained by direct end-capping of living oligo(2-ethyl-2-oxazoline) chains with in situ formed triethylammonium methacrylate. The macromonomers were subsequently polymerized in a controlled manner using the reversible addition−fragmentation chain transfer (RAFT) polymerization technique yielding a series of comb polymers with varying side chain length and backbone length. In addition, a series of graft copolymers were prepared by copolymerizing OEtOxMA with methyl methacrylate (MMA, 40−80 mol %). The copolymers were characterized by 1H NMR spectroscopy, size exclusion chromatography (SEC), and, partially, by matrix-assisted laser desorption ionization (MALDI-TOF) mass spectrometry. The LCST behavior of aqueous polymer solutions was investigated by turbidity measurements revealing cloud points that can be tuned from 35 to 80 °C by variation of the MMA content.

Collagen adsorption and structure on polymer surfaces observed by atomic force microscopy

The structure and adsorption patterns of type I and type III collagen were imaged on various polymer substrates with atomic force microscopy. Type I collagen had higher adsorption on polystyrene than on a series of polymethacrylates and formed a network of tightly, interwoven strands. Upon adsorption to different polymethacrylates, with varying side chain lengths, the collagen molecules formed long, branching fibrils. Types I and III collagen had different adsorption patterns, in some cases, on the identical substrate material. For example, instead of forming a tightly packed network, type III forms long, branching fibers on the polystyrene surface. On other materials, such as poly( n-butyl methacrylate), the two types of collagen showed similar adsorption pattern and structure. Adsorbed collagen was also imaged on various blends of polystyrene and polymethacrylates to determine how the polymer surface chemical structure and surface topography mediates protein adsorption.

Applying Linear Interaction Energy Method for Rational Design of Noncompetitive Allosteric Inhibitors of the Sarco- and Endoplasmic Reticulum Calcium-ATPase

Noncompetitive inhibitors of sarco- and endoplasmic reticulum calcium-ATPase (SERCA) have important therapeutic value in the treatment of cancer, due to their ability to induce apoptosis in cancer cells in a proliferation-independent manner. Thapsigargin (TG) and its analogues are one such class of inhibitors that bind to a hydrophobic pocket located in the transmembrane region of SERCA near the biomembrane surface and interfere with calcium transport. The binding free energies of thapsigargin-based inhibitors of SERCA were computed using a novel linear interaction energy (LIE) method with a surface generalized Born (SGB) continuum solvation model. A training set of 20 TG analogues was used to build a binding affinity model for estimating the free energy of binding for 18 new inhibitors with a root-mean-square (rms) error of 1.36 kcal/mol with respect to experimental data. For 15 out of the 18 inhibitors in the test set, the rms error was 1.02 kcal/mol, which is on the order of the accuracy level achieved by highly rigorous free energy of perturbation (FEP) or thermodynamic integration (TI) methods. On the basis of the analysis of the binding cavity at the interface of the membrane surface and the cytoplasmic region, we propose that side chains of TG derivatives at the O-8 position orient toward the cytoplasmic region through a hydrophobic channel. On the basis of this insight, four analogues of varying side chain length at the O-8 position with a charged moiety at the end were designed, tested with LIE methodology, and then validated experimentally for their SERCA inhibition activity. Low levels of rms error for the majority of inhibitors establish the structure-based LIE method as an efficient tool for generating more potent and specific inhibitors of SERCA by testing rationally designed lead compounds based on thapsigargin derivatization.

Synthesis and solid state structures of macromolecular cylindrical brushes with varying side chain length

Cylindrical brushes with a macromolecular backbone and well-defined side chains of different length (4≤ P n sc≤38) were synthesized by polymerization of macromonomers. The effect of side chain length on the intermolecular order has been investigated by means of X-ray scattering on the melt-extruded samples. The increase of the side chain molar mass results in an increase of the intermolecular distance d according to d∼( M n sc) 0.476. The contour length of the cylindrical brush polymers per main chain monomer unit, l m, was determined to slightly vary with side chain molar mass M n sc according to l m∼( M n sc) 0.059. The resulting values are much less than the maximum extension, l m =0.25 nm, which is found to be almost independent of side chain molar mass. Also, supermolecular structure formation of a random copolymer brush prepared by radical copolymerization of methacryloyl end functionalized polyvinylpyridine and polymethylmethacrylate macromonomers has been observed and is interpreted as a consequence of intramolecular phase separation.

Transport of gases and vapors in methacrylic copolymers of varying side chain length

The gas transport properties of copolymers of dodecyl methacrylate with ethyl methacrylate and hydroxypropyl methacrylate have been studied. The diffusion, solubility and permeability of oxygen, nitrogen, carbon dioxide, methane, ethane and ethylene have been measured in the temperature range 0–50 °C, and activation energies and heats of solution have been obtained. A comparison with the data available in the literature on acrylates and other methacrylates of varying aliphatic side chain length has been performed. The diffusion coefficient of gases increases with the side chain length in a way similar to that found for homologous acrylates. A representation of log( D) as a function of the inverse of the fractional free volume shows that all acrylates and methacrylates of lineal alkyl side chain fall on the same straight line.