Number-average Degree Of Polymerization Research Articles

Metallopolymer-Peptide Hybrid Materials: Synthesis and Self-Assembly of Functional, Polyferrocenylsilane-Tetrapeptide Conjugates

Conjugates of poly(ferrocenyldimethylsilane) (PFDMS) with Ac-(GA)(2)-OH, Ac-A(4)-OH, Ac-G(4)-OH and Ac-V(4)-OH have been prepared by reaction of the tetrapeptide units with the amino-terminated metallopolymer. The number average degree of polymerisation (DP(n)) of the PFDMS was approximately 20 and comparable materials with shorter (DP(n) ≈ 10) and/or amorphous chains have been prepared by the same procedure. Poly(ferrocenylethylmethylsilane) (PFEMS) was employed for the latter purpose. All conjugates were characterised by GPC, MALDI-TOF MS, NMR and IR spectroscopy. With the exception of Ac-V(4)-PFDMS(20), all materials exhibited some anti-parallel β-sheet structure in the solid state. The self-assembly of the conjugates was studied in toluene by DLS. The vast majority of the materials, irrespective of peptide sequence or chain crystallinity, afforded fibres consisting of a peptidic core surrounded by a PFS corona. These fibres were found in the form of cross-linked networks by TEM and AFM. The accessibility of the chemically reducing PFS corona has been demonstrated by the localised formation of silver nanoparticles on the surface of the fibres.

Comb-shaped graft copolymers with cellulose side-chains prepared via click chemistry

Abstract Comb-shaped copolymers with cellobiose acetate or cellulose triacetate (CTA) side-chains, PPMA-g-(CTA2-C15) and PPMA-g-(CTA13-C15), were prepared by grafting N-(15-azidopentadecanoyl)-2,3,6-tri-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-β- d -glucopyranosyl)-β- d -glucopyranosylamine (CTA2-C15-N3) and N-(15-azidopentadecanoyl)-tri-O-acetyl-β-cellulosylamine (CTA13-C15-N3, number average degree of polymerization (DPn) = 13) onto poly(2-propyn-1-yl methacrylate) (PPMA, weight average degree of polymerization (DPw, X + Y = 5.59 × 102)) via “click chemistry”. The copolymers were characterized by 1H, 13C and two-dimensional NMR and size exclusion chromatography–multi-angle laser light scattering (SEC–MALS) measurements. The numbers of CTA side-chains (X) of PPMA-g-(CTA2-C15) and PPMA-g-(CTA13-C15) were calculated as 4.03 × 102 and 2.45 × 102, respectively. Copolymers with cellulosic side-chains, PPMA-g-(CELL2-C15) and PPMA-g-(CELL13-C15), were successfully obtained after deacetylation of PPMA-g-(CTA2-C15) and PPMA-g-(CTA13-C15), respectively. X-ray diffraction measurements revealed that PPMA-g-(CELL13-C15) showed crystalline pattern of cellulose II, which is believed to have anti-parallel orientation.

Orthogonal chain length control in calix[5]arene-based AB-type supramolecular polymers

New AB-type supramolecular polymers have been prepared by acid-promoted self-assembly of an aminododecyloxy-calix[5]arene monomer precursor. The number-average degree of polymerization has been found to be dependent on the concentration of the salt monomer and on the nature of the counterion (i.e., chloride, picrate or hexafluorophosphate).Chain-length regulation experiments have been carried out, employing orthogonal chain stoppers capable of selectively interacting with a given moiety of the AB-type monomer/polymer. Competitive calix[5]arene ‘caps’ and n-butylammonium ion ‘plugs’ have been used to control the extent of self-assembly of the polymer, in turn interacting with the ammoniumdodecyloxy or with the cavity end-groups of the supramolecular calixarene assembly. These experiments, conveniently carried out at a 10mM concentration, can be easily followed by 1H NMR spectroscopy.

Kinetic treatment for the copolycondensation of A 2 and CB 2 monomers with non-equal reactivity

The kinetics of copolycondensation of A 2 and CB 2 monomers with non-equal reactivity was investigated in detail. The analytical expressions of the molecular size distribution function, the average degree of polymerization, and the polydispersity index of the products obtained were derived. The gelation may take place in the range of the monomer feed ratio ( λ) of A 2 to CB 2 from 3/4 to 3 if the reactivity ratio ( r) of C to B group is 1. The range may be reduced slightly to 3 / 2 ≤ λ ≤ 3 for enough high r. High reactivity ratios are beneficial to enhance the conversion of A groups and the number average degree of polymerization at the critical point of gelation. The high weight average degree of polymerization but low number average degree of polymerization at the critical point should attribute to the reason that the larger the species formed in the reaction system, the faster its growth. A number of oligomer species are present at the critical point. Gelation may be avoided if a suitable feed ratio is used. The wide molecular weight distribution also may be improved if excluding the residual monomers and the small oligomer species.

Alkyl β-d-cellulosides: non-reducing cellulose mimics

Non-reducing cellulose mimics, termed alkyl β-d-cellulosides, were successfully prepared by two efficient multi-step syntheses starting from commercially available microcrystalline cellulose or cellulose triacetate. Introduction of the alkoxy moiety and degradation of the cellulose backbone was carried out in the presence of a Lewis acid, on one hand. On the other hand, cellulose hydrolysis mediated by mineral acids was combined with β-glycosidation performed in the presence of silver salts. The samples obtained possess a number-average degree of polymerization from 5 to 25, determined by size-exclusion chromatography, elemental analyses, NMR spectroscopy, and MALDI-TOF mass spectrometry. Samples in multi-gram quantities were available. Selective formation of a β-glycosidic bond between the C-1 atom of the reducing end group and alkoxy moieties was confirmed by a combination of 2D NMR spectroscopic and MALDI-TOF MS techniques. Due to the blocking of the aldehyde function, the cellulosides described are very useful mimics for the investigation of polysaccharide interactions with other complex molecules such as proteins or to determine polymer properties in solution or in solid state.

Influence of Solvent Polarity on the Self-Assembly of the Crystalline–Coil Diblock Copolymer Polyferrocenylsilane-b-polyisoprene

Many poly(ferrocenyldimethylsilane) (PFS) block copolymers form fiber-like micelles with a semicrystalline core in selective solvents. Solvent effects on micelle formation are not well understood. This paper compares micelle formation for a sample of PFS50–PI1000 (the subscripts refer to the number-average degrees of polymerization) in decane with that in tert-butyl acetate (tBA), a more polar solvent. When micelle formation is seeded, by adding block copolymer as a concentrated solution in tetrahydrofuran to solutions of micelle fragments, micelle growth was similar in both solvents. Micelles with a narrow length distribution were formed and the length increased in proportion to the amount of polymer added. In contrast, when micelles were prepared by heating a sample of the block copolymer in decane or tBA to 90 °C and allowing the solution to cool, pronounced differences were observed. In decane, micelles with a uniform width (10 nm) and a length on the order of 5 μm formed after 1 h, and grew to about ...

Flow Instability of Polyvinyl alcohol)/Dimethyl Sulfoxide Solution under Steady Shear

The effects of solution temperature and molecular weight on the rheological responses of poly(vinyl alcohol) (PVA) semidilute solutions (13 g/dL- 19 g/dL) in dimethyl sulfoxide (DMSO) have been studied using PVA with two different number-average degrees of polymerization (Pn): 1700 and 4000. For the rheological experiments using dynamic shear, the PVA solution with a Pn of 1700 showed rather simple Newtonian fluid behaviour, whereas that with Pn of 4000 exhibited non-Newtonian shear thinning behaviour. Steady shear rheology experiments suggested that the lower Pn PVA solutions were Newtonian fluids, which is consistent with the dynamic shear rheology results. However, an abrupt decrease of shear viscosity at high shear rates was observed for the higher Pn PVA solutions at lower temperatures, such as 30 °C and 50 °C. At higher temperatures of 70 °C and 90 °C, the higher molecular weight PVA solutions exhibited simple shear thinning behaviour without any further complications of flow instability. The fact that temperature plays a critical role in controlling the observed flow instability of the PVA solutions in DMSO strongly suggests that there exist enhanced inter-chain interactions by hydrogen bonding of PVA chains beyond the chain entanglements, particularly for the higher Pn PVA semidilute solutions at low temperatures. Therefore, it is important to consider both chain entanglements and hydrogen bonding interactions in order to process PVA solutions without causing undesirable flow instability.

Synthesis of diblock copolymers with cellulose derivatives 4. Self-assembled nanoparticles of amphiphilic cellulose derivatives carrying a single pyrene group at the reducing-end

Self-assembled cellulose-pyrene nanoparticles were prepared from amphiphilic cellulose derivatives carrying a single pyrene group at the reducing-end, N-(1-pyrenebutyloyl)-β-cellulosylamine (CELL13Py and CELL30Py, the number average degrees of polymerization (DPn) of 13 and 30, respectively) and N-(15-(1-pyrenebutyloylamino)-pentadecanoyl)-β-cellulosylamine (CELL13C15Py and CELL30C15Py, DPn of 13 and 30, respectively). Transmission electron microscopy (TEM) observation revealed that CELL13C15Py and CELL30C15Py formed self-assembled nanoparticles with the average diameters of 108.8 and 40.0 nm, respectively. The average radius of CELL30C15Py nanoparticles (20.0 nm) agreed well with the molecular length of its cellulose chain (19.2 nm). CELL30C15Py nanoparticles were expected to have monolayered structure, consisting of cellulose shell with radial orientation and hydrophobic core of 15-(1-pyrenebutyloylamino)-pentadecanoyl groups. The fluorescent spectrum of CELL30C15Py nanoparticles showed an excimer emission due to dimerized pyrene groups, indicating that the pyrene groups at the reducing-end of cellulose are associating in the particles. The balance of hydrophilic and hydrophobic parts of the cellulose derivatives controlled their self-assembled nanostructures. X-ray diffraction measurements revealed that radially oriented cellulose chains of CELL30C15Py nanoparticles were mostly amorphous, and at the same time exhibited weak reflection pattern of cellulose II, which is believed to have anti-parallel orientation.

Water-soluble low-molecular-weight cellulose chains radially oriented on gold nanoparticles

Cellulose chains bearing N-lipoyl group at the reducing-end as a sulfide linker, self-assembled on the surface of gold nanoparticles (CELL2Au, CELL13Au, and CELL41Au with the number average degrees of polymerization (DPn) of 2, 13, and 41, respectively) were prepared. CELL2Au, CELL13Au, and CELL41Au were obtained via deprotection of the cellulose triacetate (CTA) self-assembled on the surface of gold nanoparticles that are consisting of CTA chains with corresponding DPn organized in a radial manner with head-to-tail orientation, where a head is the reducing-end, and a tail is the non-reducing-end. CELL2Au and CELL13Au were well-dispersed in water including a trace of methanol, whereas CELL41Au was not. The transmission electron microscopy (TEM) observation of CELLAus deposited on copper grids revealed that the diameters (d) of the gold cores of CELL2Au, CELL13Au, and CELL41Au were 6.1, 6.1, and 11.5 nm, respectively. Wide angle X-ray diffractgram showed that cellulose chains of CELL13Au had quite low crystallinity and exhibited additional faint diffraction pattern of cellulose II. Cellulose chains of CELL41Au were amorphous. The UV–vis measurements revealed that CELL2Au and CELL13Au were well-dispersed in water. The hydrodynamic diameters (D) of CELL2Au and CELL13Au in water were 21.8 and 55.9 nm, respectively, according to dynamic light scattering (DLS) measurements, suggesting that cellulose chains on the gold were organized in a radial manner with head-to-tail orientation. 1H-NMR measurement revealed that low-molecular-weight cellulose chains (DPn = 13) on the gold dissolved in water, whereas low-molecular-weight cellulose (DPn = 13) itself did not.

Thermogravimetry of the products in an imbalance condensation of an aromatic diamine and dichloride

Imbalance condensation of diaminophenylbenzimidazole, DAPBI, with terephthaloyl chloride, TPC was conducted for the purpose of synthesis of macromonomers, expected to be used in syntheses of aromatic polyamides with structural regularities. The products are soluble in dimethylsulfoxide—d6, and their 1H NMR spectra indicate that all the products are carboxyl-terminated. The signal of carboxyphenyl linked to chain ends is different from that of terephthaloyl in the 1H NMR spectra. By use of the ratio of the signal intensity of the former to that of the latter, the number-average degree of polymerization, DPNMR is determined. With the mole ratio in feed, DPNMR of the product increases. The TG thermograms of the products are a multistage one. Each stage is classified by temperature and mass loss at an inflection point. Mass loss of each stage classified by temperature at an inflection point corresponds to mass fraction of an aromatic amide with a characteristic degree of polymerization, DP, and that is, the DP distribution of the products is roughly estimated from the TG thermograms. The DP distribution of macromonomers influences performance of aromatic polyamides with structural regularities, derived from the macromonomers. The convenient estimation method of DP distribution by TG is useful in industries of high-performance polymers. To the knowledge, such convenient technique has never reported.

Monte Carlo simulation on kinetic behavior of one-pot hyperbranched polymerization based on AA*+CB2

Monte Carlo simulation was applied to investigate the kinetic behavior of AA*+CB2 system. The algorithm consisted of two procedures to simulate the in-situ synthesis of AB2-like intermediate and the subsequent polymerization, respectively. In order to improve the accuracy of the prediction, the mobility distinction between different scale molecules in polymerization was taken into account by relating the reaction rate constants to the collision possibility of each pair of species. The feed ratio of initial monomers and the activity difference between the two functional groups within AA* were studied systematically to catch the essential features of the reaction. Simulation results have revealed that the achievable maximum conversion primarily depends on the extent of the reactivity difference between A and A*-groups, and it is suggested that A*-group should be at least 10 times more active than A-group to achieve high number-average degree of polymerization.

Proton transport properties of poly(aspartic acid) with different average molecular weights

We synthesized seven partially protonated poly(aspartic acids)/sodium polyaspartates (P-Asp) with different average molecular weights to study their proton transport properties. The number-average degree of polymerization (DP) for each P-Asp was 30 (P-Asp30), 115 (P-Asp115), 140 (P-Asp140), 160 (P-Asp160), 185 (P-Asp185), 205 (P-Asp205), and 250 (P-Asp250). The proton conductivity depended on the number-average DP. The maximum and minimum proton conductivities under a relative humidity of 70% and 298 K were 1.7 · 10 −3 S cm −1 (P-Asp140) and 4.6 · 10 −4 S cm −1 (P-Asp250), respectively. Differential thermogravimetric analysis (TG-DTA) was carried out for each P-Asp. The results were classified into two categories. One exhibited two endothermic peaks between t = (270 and 300) °C, the other exhibited only one peak. The P-Asp group with two endothermic peaks exhibited high proton conductivity. The high proton conductivity is related to the stability of the polymer. The number-average molecular weight also contributed to the stability of the polymer.

Self-Assembly of Colloidal Quantum Dots on the Scaffold of Triblock Copolymer Micelles

This paper describes the co-self-assembly of a polystyrene-poly(4-vinylpyridine)-poly(ethylene oxide) triblock copolymer with CdSe nanocrystals (quantum dots, QDs) and with a styrene compatible phenylenevinylene conjugated polymer (MEH-PPV) in mixtures of chloroform and 2-propanol. The polymer itself (PS(577)-P4VP(302)-PEO(852), where the subscripts refer to the number average degree of polymerization) forms worm-like micelles when 2-propanol is added to a solution of the polymer in CHCl(3). In the presence of increasing amounts of QDs, the structures become shorter and form only spherical hybrid micelles (with QDs bound to the surface) at 4:1 QD/polymer w/w, accompanied by free QDs. These structures retain their colloidal stability in 2-PrOH, suggesting that even the free QDs bear a surface shell of block copolymer. The presence of MEH-PPV has no affect on this self assembly. One of the most remarkable observations occurred when the samples in 2-PrOH were centrifuged to remove the free QDs accompanying the hybrid micelles. The micelles sedimented, but upon redispersion in 2-PrOH, rearranged to form colloidally stable long branched cylindrical structures including cylindrical networks.

Aqueous solution self-assembly of polystyrene-b-poly(l-lysine) diblock oligomers

This paper reports on the dilute, aqueous solution self-assembly of two asymmetric polystyrene-b-poly(l-lysine) (PSnPKm) diblock oligomers with PS and PK number-average degrees of polymerization of eight, respectively, 40 and 60. The self-assembly of these diblock oligomers was investigated using static and dynamic light scattering in combination with analytical ultracentrifugation. Direct dissolution of the diblock oligomers in water generates a mixture of solution assemblies, part of which is cylindrical or rod-like in nature according to the light scattering experiments. This is surprising given the highly asymmetric nature of the diblock oligomers. Additional experiments in which the sample preparation conditions were varied and sample solutions subjected to a thermal treatment or prepared via dialysis from an organic/aqueous solution, however, suggest that direct dissolution results in kinetically trapped assemblies, which are (partially) converted into thermodynamically more favored assemblies upon varying the sample preparation conditions.

Preparation of Recycled Polyvinyl Alcohol) (PVA)/Iodine Polarizing Film

To precisely identify the effect of preparation conditions on the polarizing efficiency (PE) of recycled poly(vinyl alcohol) (PVA)/iodine complex film, PVA film and PVA/iodine polarizing film were prepared by using recycled nonwoven PVA with a number-average degree of polymerization (Pn) of 1700, syndiotactic diad (s-diad) content 54.6%, and degree of saponification (DS) 97.6%. We investigated the effects of various conditions such as soaking time, temperature of I2/KI aqueous solution, draw ratio, and temperature of aqueous boric acid solution on the transmittance and PE of recycled PVA/iodine complex film. Maximum transmittance and PE values of recycled PVA/iodine complex film were 41.2% and 99.8%, respectively. It was found that the recycled PVA/iodine polarizing film showed effective transmittance and PE values comparable with those of commercial PVA/iodine polarizing film.

Numerical modeling of polystyrene synthesis in coiled flow inverter

Recent studies show that microfluidic devices are gaining importance as micromixer in chemical and bio-chemical analysis systems. However, little attention has been paid to investigate chemical reactions such as polymerization reaction process in microreactors. In the present study, numerical modeling of the free-radical polymerization of styrene was carried out in novel coiled flow inverter (CFI) microreactor. The concept of CFI is based on the technique developed by Saxena and Nigam (AlChE J 30:363–368, 1984). This device is made up of helical coiled tube which is bent periodically to 90° at equidistant length. The CFD modeling for polymerization reaction taking place in coiled tube reactor was also performed in order to understand the influence of secondary flows on reactor performance for fluid flowing with very low flow rate. Its performance was compared with CFD results obtained in a straight tube reactor having identical length and operating under the same process conditions. The results showed that monomer conversion in the coiled tube reactor was higher than that of the straight tube reactor. Further work was carried out in the novel CFI reactor to study the effect of diffusion coefficient and number of bends on different parameters such as monomer conversion, number-average degree of polymerization (DP n ), and polydispersity indexes (PDI). It was found that the performance of CFI as reactor increased when the diffusion coefficients of reactants was decreased. Thus, CFI was found to be an efficient microfluidic device for controlling the free-radical polymerization.

Radially oriented cellulose triacetate chains on gold nanoparticles

Cellulose triacetate (CTA) derivatives having a disulfide group at the reducing-end (CTA2S, CTA13S, CTA41S), with number average degrees of polymerization (DPns) of 2, 13 and 41, respectively, were prepared. The CTA-self-assembled gold nanoparticles (CTA2Au, CTA13Au, and CTA41Au) were obtained through the reduction of gold salt (HAuCl4) with CTASs. The diameters (d) and the interparticle distances (L) of the gold cores were analyzed by transmission electron microscopy (TEM) observations. The d values of CTA2Au, CTA13Au, and CTA41Au, were 8.7, 7.9, and 13.4 nm respectively. The L values of CTA2Au, CTA13Au, and CTA41Au, were 2.8, 6.3, and 20.9 nm, respectively, and agreed well with the molecular length (l) of CTAS chains (ls of CTA2S, CTA13S, CTA41S = 2.0, 7.5, 21.5 nm, respectively). The hydrodynamic diameters (D) of CTAAu nanoparticles in chloroform solution, measured by dynamic light scattering (DLS), were larger than the d values and increased with the increase in the molecular length of the CTA chains. The CTAS chain was found to work as an excellent stabilizer of the gold nanoparticles in both solid state and solution. The molecular length of CTA chains controlled the size and the alignment of the gold nanoparticles. As a result, the radially oriented CTA chains on the gold nanoparticles were successfully prepared.

Homogeneous methylation of wood pulp cellulose dissolved in LiOH/urea/H 2O

Spruce sulphite cellulose (number average degree of polymerization 620) dissolved in an aqueous solution of 8% (w/w) LiOH*H 2O and 12% (w/w) urea was methylated with dimethyl sulphate (DMS). By varying the reaction temperature between 22 and 50 °C, the molar ratio between 9 and 15 mol DMS per mol anhydroglucose unit, and the reaction time from 4 to 24 h, methyl cellulose (MC) with degree of substitution (DS) values in the range of 1.07 and 1.59 was prepared. The chemical structure of MC was analysed by FTIR and 1H NMR spectroscopy. The turbidity (given in nephelometric turbidity units, NTU) of the aqueous solution of MC reached an optimum of 10 NTU for a product obtained with 12 mol DMS/mol AGU at 50 °C. GPC measurements revealed polymer degradation to a certain extent. The intrinsic viscosity and the Huggins constant k of the MC samples increased with increasing DS value. The MC samples possess k values higher than 0.8, indicating association of the polymer chain. The zero-shear viscosity decreased with increase of both temperature and the amount of methylation agent due to the depolymerization. During the heating/cooling cycle (20–90 °C) of the aqueous solutions of MC, it was observed that samples synthesized at 22 °C with DS values lower than 1.3 did not undergo phase separation in aqueous solution. Phase separation hysteresis with a precipitation temperature up to 80 °C was obtained for aqueous solutions of MC with DS values between 1.07 and 1.66 synthesized at higher temperatures. The functionalization pattern determined by GLC of the corresponding partially methylated glucitol acetates is close to randomness and comparable with those of commercial MC samples.

Sphere-to-Wormlike Network Transition of Block Copolymer Micelles Containing CdSe Quantum Dots in the Corona

Poly(styrene-b-4-vinylpyridine) (PS404-b-P4VP76, where the subscripts refer to the number-averaged degree of polymerization) forms spherical crew-cut micelles with a PS core and a P4VP corona when 2-propanol is added to a solution of the polymer in chloroform. When the CHCl3 solution also contains CdSe quantum dots, hybrid micelles form with the QDs bound to the corona. Here we report that vigorous magnetic stirring of a solution of these hybrid micelles in a solution containing 73 vol % 2-propanol leads to a morphology transformation to form three-dimensional wormlike networks that have structural features similar to that first reported by Jain and Bates [Science 2003, 300, 460−464] for a poly(butadiene-b-ethylene oxide) block copolymer in water. Under the influence of shear, PS404-b-P4VP76 micelles appear to aggregate and then rearrange to form colloidally stable networks consisting of wormlike micelles, uniform in width, that are present as loops and tails connected by T- and Y-junctions. The wormlike micelles are similar in width to the original hybrid micelles, whereas the tails of the micelles have thicker bulbous end-caps. This morphology transition is extremely sensitive to solvent composition and is also affected by the stirring rate.

Synthesis and Structure/Property Relationships of Regioselective 2-O -, 3-O - and 6-O -Ethyl Celluloses

Regioselectively ethylated celluloses, 2-O- (1), 3-O- (2), and 6-O-ethyl- (3) celluloses were synthesized via ring-opening polymerization of glucopyranose orthopivalate derivatives. The number-average degrees of polymerization (DP(n)s) of compounds 1 and 2 were calculated to be 10.6 and 49.4, respectively. Three kinds of compound 3 with different DP(n)s were prepared: DP(n)s = 12.9 (3-1), 60.3 (3-2), and 36.1 (3-3). The 2-O-, 3-O-, and 6-O-ethylcelluloses were soluble in water, confirmed by NMR analysis. Furthermore, the 3-O- (2), and 6-O-ethyl- (3-2) celluloses showed thermo-responsive aggregation behavior and had a lower critical solution temperature (LCST) at about 40 degrees C and 70 degrees C, respectively, based on the results from turbidity tests and DSC measurements. The 6-O-ethyl-cellulose (3-3) with DP(n) = 36.1 and DP(w) = 54.6 showed gelation behavior over approx 70 degrees C, whereas the 6-O-ethyl-celluloses 3-1 and 3-2 with lower and higher molecular weight, such as DP(n)s 12.9 and 60.3, did not show gelation behavior at this temperature. It was revealed that the position of ethyl group affected the phase transition temperature. According to our experiments, the 3-O-ethyl and 6-O-ethyl groups along the cellulose chains caused the thermo-responsive property of their aqueous solutions. The appropriate DP of the regioselective 6-O-ethyl-cellulose existed for gelation of the aqueous solution.