Molecular weight determination of 83% degree of decetylation chitosan with non‐Gaussian and wide range distribution by high‐performance size exclusion chromatography and capillary viscometry

Molecular weight determination of 83% degree of deacetylation (DD) chitosan with non‐Gaussian and broad molecular weight distribution by high‐performance size exclusion chromatography (HPSEC) and by capillary viscometry were proposed. The relationships between weight average retention volumes (RVw) of HPSEC and intrinsic viscosities ([η]) measured by capillary viscometer and the weight average molecular weight (Mw) measured by static light scattering were established for routine molecular weight determination of chitosans either by HPSEC or by the capillary viscometry method, respectively. These results showed: relationships of RVw and Mw for different Mw of 83.0% DD chitosans can be expressed by the equation Log Mw = −0.433 RVw + 11.66. The RVw of other DD chitosans do not correlate well with this equation. It indicated that DD of chitosan affected the relationship of RVw and Mw of chitosans studied. The Mark–Houwink constant a decreased from 0.715 to 0.521, as the solution ionic strength increased from 0.01M to 0.30M, whereas constant k increased from 5.48 × 10⁻⁴ to 2.04 × 10⁻³ over the same range of ionic strength solutions. The established RVw and Mw equation and [η] and Mw equation (Mark–Houwink equation) can be routinely used to determine the molecular weight from RVw or [η] of chitosan by HPSEC or by capillary viscometer, respectively, without the need of expensive instrumentation. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1905–1913, 1999     

Relationship between molecular structure and moisture‐retention ability of carboxymethyl chitin and chitosan

Carboxymethyl chitins and chitosans (CM‐chitins, CM‐chitosans) of different substitution sites were prepared under different reaction conditions, and partially depolymerized carboxymethyl chitins of various molecular weights from 24.8 × 10⁴ to 0.26 × 10⁴ were obtained by degrading with chemical reagents. Degree of substitution (DS) was estimated by potentiometric titration. Substitution site was confirmed by infrared and ¹³C‐NMR spectra. Molecular weights were determined with gel permeation chromatography and gel permeation chromatography combined with laser light scattering (GPC‐LLS). Moisture‐absorption and retention abilities of these compounds were tested in comparison with those of hyaluronic acid (HA). The results reveal that 6‐carboxymethyl group in the molecular structure of chitin and chitosan is a main active site responsible for moisture retention. Although carboxymethylation at OH‐3 and N position is not essential, they contribute to the ability. Moisture‐retention ability is also related to molecular weight; that is, higher molecular weight helps to improve moisture‐retention ability. 6‐O‐CM‐chitin (chitosan) with a DS above 0.8 and molecular weight higher than 24.8 × 10⁴ has the potential to substitute for HA for use in cosmetics and clinical medicine. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1233–1241, 2002     

Free radical scavenging activity of cellulase‐treated chitosan

Partially N‐acetylated chitosan was hydrolyzed by the cheap, commercially available, and efficient cellulase. The products, with different molecular weight, were comparatively investigated by GPC, FT‐IR, XRD, and NMR. The results show that the decrease of molecular weight led to transformation of crystal structure and increase of water‐solubility, but the chemical structures of residues were not modified. Superoxide anion radical and hydroxyl radical quenching assay were used for the evaluation of free radical scavenging activity of cellulase‐treated chitosan in vitro. Low molecular weight chitosan (LMWC3, M_w 1.7 × 10³) exhibited high scavenging activity against free radical. It scavenged 79.3% superoxide radical at 0.1 mg mL^?1. At 2.0 mg mL^?1, scavenging percentage of initial chitiosan, LMWC1 (M_w 27.3 × 10³), LMWC2 (M_w 5.9 × 10³), and LMWC3 (M_w 1.7 × 10³) against hydroxyl radical was 14.3%, 33.1%, 47.4%, and 65.9%, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Acid hydrolysis of commercial chitosans

Commercial chitosans were subjected to controlled acid hydrolysis and their degrees of deacetylation (DD), molecular size and rheological flow profiles determined (pre‐ and post‐hydrolysis) by ¹H‐NMR spectroscopy, high‐performance size‐exclusion chromatography and rheometry, respectively. Hydrolysis resulted in DD increases between 4 and 11%. Unhydrolysed chitosans had M_w and M_n values in the ranges 700–1200 and 130–210 kDa, respectively. Chitosan with the smallest initial molecular size averages had the smallest averages after hydrolysis; however, a chitosan with an intermediate initial molecular size proved to be most resistant to hydrolysis. Molecular size trends were paralleled by zero shear viscosity (η₀) measurements determined by application of the Williamson model to rheological flow profile data. Viscosity is obviously related to molecular size, but does not necessarily reflect relative ease of hydrolysis, since specific hydrolysis conditions affect structurally similar polysaccharides in different ways (in terms of rate of depolymerisation and de‐N‐acetylation, etc), which are not simply due to differences in molecular size profiles pre‐hydrolysis. Copyright © 2005 Society of Chemical Industry     

Microbiocidal activity of chitosan‐N‐2‐hydroxypropyl trimethyl ammonium chloride

Chitosan‐N‐2‐hydroxypropyl trimethyl ammonium chloride (QTS) was prepared by reaction of chitosan with glycidyl trimethylammonium chloride, which was characterized by FTIR. QTS with different molecular weights (M_w 41.55 × 10⁴, 9.02 × 10⁴, 3.57 × 10⁴, and 0.17 × 10⁴) showed biocidal activity on Staphylococcua aureus, Bacillus subtilis, Staphylococcua epidermidis, and Candida albicans. QTS with high molecular weight had high biocidal activity on the gram‐positive bacteria, and the biocidal effect of QTS decreased with decreasing molecular weight from 9.02 × 10⁴ to 0.17 × 10⁴. QTS with M_w 41.55 × 10⁴ exhibits slightly lower biocidal activity on Candida albicans than other QTS samples. However, no remarkable biocidal activity of QTS was found on gram‐negative bacteria Escherichia coli and Pseudomonas aeruginosa at the concentration up to 10 g L^?1. Existence of cationic surfactant, amphoteric surfactant, nonionic surfactant, Ca²⁺ and Mg²⁺ had no remarkable effect on microbiocidal activity of these QTS samples. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3851–3856, 2007     

Effect of recovery methods and conditions on the yield,solubility, molecular weight,and creep compliance of regenerated chitosan

The objective of this study is to explore the effect of using different recovery methods and conditions on the yield, solubility, molecular weight, and creep compliance of the regenerated chitosan. The results show that yields obtained by dialysis were higher than those using recovery medium of alkali solutions, organic solvents, or alkali–alcohol–water mixtures. For those chitosans employing alkali solutions as the recovery medium, the higher the alkali concentration used, the higher the yields obtained, although the total quantity of alkali in the solution were the same. Solubilities of regenerated chitosans were similar and independent at the methods of using alkali solution, organic solvent or alkali–alcohol–water mixture or at different concentrations of alkali solution. The molecular weight of regenerated chitosan decreased from 2.37 × 10⁷ to 1.68 × 10⁷ Da proportionally with the concentration of the alkali solution of the recovery medium from 1N to 8N. Creep compliance of regenerated chitosan gel obtained from 65% degree of deacetylation (DD) chitosan was lower than that of either 72 or 89% DD chitosan gel. Of the same DD chitosan, compliance of regenerated chitosan gels obtained by using a higher concentration of alkali solution was lower than that of a lower concentration ones. Hydrogels regenerated from different DD chitosans and/or different recovery mediums have different structure and tactile properties. Therefore, they can be used as wound dressings suited to different applications. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 193–202, 2002; DOI 10.1002/app.10296     

An amphoteric water‐soluble copolymer. II. Effect of its molecular weight on the dispersion of barium titanate in water

An amphoteric water‐soluble copolymer, that is, polyacrylamide/(α‐N,N‐dimethyl‐N‐acryloyloxyethyl)ammonium ethanate (PAAM/DAAE) was synthesized and it showed the ability to disperse BaTiO₃ (BT) particles in aqueous solutions. In this work, the effect of molecular weight of this polymer on the dispersing properties was further examined. The results indicate that the effectiveness of three polymer samples with different molecular weights in the dispersion of BT particles is P2 (M_w = 1.1 × 10⁵) > P1 (M_w = 1.2 × 10⁴) > P3 (M_w = 3.0 × 10⁵). Apparently, P2 is most effective in dispersing the particles, reducing the viscosity of the suspensions, and obtaining highest green and sintered densities. This is attributed to the highest adsorption of this polymer onto BT powder, and causes strongest electrostatic and steric repulsions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 886–891, 2006     

Effects of ionic strength and pH on the diffusion coefficients and conformation of chitosans molecule in solution

The effects of ionic strength and pH on the diffusion coefficients and gross conformation of chitosan molecules in solution were studied. Chitosan with 83% degree of deacetylation (DD) was prepared from red shrimp (Solemocera prominenitis) processing waste. Ten different molecular weight chitosans were prepared by ultrasonic degradation, and their molecular weights were determined by static light scattering. The weight-average molecular weight (M_w) were between 78 to 914 kilo dalton (KDa). Solution of different ionic strengths (I = 0.01, 0.10, and 0.20) but the same pH (2.18) and different pHs (2.37, 3.10, and 4.14) but the same ionic strength (I = 0.05) were prepared to measure their mutual diffusion coefficient (D_m). The diffusion coefficients for standard condition (D_20,w) were derived from D_m. Intrinsic viscosities ([η]) were determined by a capillary viscometer in different pH solutions. The Mark–Houwink exponents a and ε were obtained from plots of Log [η] and Log D_20,w versus Log M_w, respectively. The results show that diffusion coefficients increased with increasing ionic strength or with increasing pH or with decreasing M_w. Value of ε and a were between 0.503 to 0.571 and ranged from 0.543 to 0.632, respectively. The results indicates that chitosans conformation were in random coil in solutions in the ranges of ionic strength and pH studied. The values of a*, ε* and a**, ε**, Mark–Houwink exponents of smaller and higher than 223 KDa chitosans, respectively, were between 0.752 to 0.988 and 0.585 to 0.777 for smaller M_w chitosans and 0.406 to 0.428 and 0.430 to 0.518 for larger M_w chitosans, respectively. Molecular-weight-induced conformational transition occurred because smaller M_w chitosans was more extended than higher M_w chitosans. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2041–2050, 1999     

Molecular weight‐dependent antifungal activity and action mode of chitosan against Fulvia fulva (cooke) ciffrri

Antifungal activities of chitosans (CTS) with different molecular weights (M_w) and different concentrations against Fulvia fulva (cooke) ciffrri (F. fulva) causing leaf mold in tomato plants were studied in vitro and in vivo; the action mode and its inhibition at different stages during the life cycle of F. fulva were observed. The results showed that: (1) in vitro, CTS exhibited strong antifungal activity against F. fulva, especially for the medium M_w (213 and 499 KDa) CTS. Almost complete inhibition of F. fulva conidia germination and mycelia colony radial growth was found when CTS was at concentration of 0.5 and 2 mg mL^?1, respectively; however, inhibitory effect on sporulation was not very obvious for all CTSs tested in this experiment. In vivo, CTS of 213 KDa CTS at 6 mg mL^?1 concentration produced stronger antifungal effect than others. (2) The morphological study by scanning electron microscope (SEM) showed that CTS could induce the hyphal swelling, and the surface of hypha which was treated with low M_w (82 KDa) chitosan was smooth, but was rough treated with high M_w (1320 KDa) chitosan. The further study using a confocal laser scanning microscopy (CLSM) coupled with fluorescein isothiocyanate (FITC)‐fluorescence detection system showed fluorescence of the FITC‐labeled chitosans of which M_ws were below 500 KDa could enter into the inner of hypha; however, 1320 KDa chitosan was blocked off the outer of hypha. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Urea‐induced conformational changes of chitosan molecules and the shift of break point of Mark–Houwink equation by increasing urea concentration

Chitosan solutions of the same 83% degree of deacetylation (DD) but different weight average molecular weights (M_ws) (78–914 kDa) in 0.01M HCl containing different concentrations of urea (0–6M) were prepared. Intrinsic viscosity ([η]) and weight average molecular weight (M_w) of chitosan were measured with a capillary viscometer and light scattering, respectively. Mark–Houwink exponent a was used as the parameter of conformational index. The Mark–Houwink exponent a increased with increasing concentrations of urea. When solutions contained 0, 2, 3, 4, and 6M urea, the value of a increased from 0.715 to 0.839, 0.894, 1.000, and 1.060, respectively. This indicates the occurrence of urea‐induced conformational transitions of chitosans. The break point shifted from 223 kDa in solutions containing no urea to 280 kDa in 2M urea solutions, to 362 kDa in 4M urea solutions and further to 481 kDa in 6M urea solutions. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 452–457, 2000     

Molecular weight and chain conformation of amylopectin from rice starch

By using laser light scattering (LS) and size exclusion chromatography combined LS, we have investigated the molecular weight and chain conformation of amylopectin from rice of India (II‐b), japonica (IJ‐b), and glutinous (IG‐b) in dimethyl sulfoxide (DMSO) solution. The weight‐average molecular weight (M_w) and radius of gyration (〈S²〉^½) of amylopectin were determined to be 4.06 × 10⁷ and 128.5 nm for India rice, 7.41 × 10⁷ and 169.6 nm for japonica rice, 2.72 × 10⁸ and 252.3 nm for glutinous rice, respectively. The 〈S²〉^½ values were much lower than that of normal polymers, indicating a small molecular volume of amylopectin, as a result of highly branched structure. Ignoring the difference of degree of branching, approximated dependences of 〈S²〉^½ and intrinsic viscosity ([η]) on M_w for amylopectin in DMSO at 25°C were estimated to be 〈S²〉^½ = 0.30M_w^0.35 (nm) and [η] = 0.331M_w^0.41 (mL g^?1) in the M_w range studied. Moreover, from the 〈S²〉^½ values of numberless fractions obtained from many experimental points in the SEC chromatogram detected with LS, the dependence of 〈S²〉^½ on M_w for the II‐b sample was estimated also to be 〈S²〉^½ = 0.34 M_w^0.347, coinciding with the above results. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Anionic polymerization of secondary aminostyrene and characterization of the polymer

Preparation by anionic living technique and characterization of poly(secondary aminostyrene) having narrow molecular weight distribution were investigated. N‐isopropyl‐N‐trimethylsilyl‐4‐vinylbenzylamine (SBA) was purified by use of sec‐butylmagnesium bromide as a purging reagent under high vacuum. SBA was anionically polymerized with n‐butyllithium or cumylpotassium in tetrahydrofuran at −78°C under high vacuum to yield the corresponding polymer (PSBA) in 100% yield. Subsequent deprotection of the trimethylsilyl group from PSBA produced poly(N‐isopropyl‐4‐vinylbenzylamine) (PBA) of the desired molecular weights (M_n: 1.3 × 10⁴–17 × 10⁴, determined by membrane osmometry) with narrow molecular weight distribution (M_w/M_n: 1.07–1.03, determined by gel permeation chromatography). The living lithium carbanion of PSBA can initiate styrene (St) to yield PSBA‐b‐PSt block copolymer (M_n = 4.0 × 10⁴, M_w/M_n = 1.05), and the polystyryllithium can initiate SBA to yield PSt‐b‐PSBA (M_n = 3.7 × 10⁴, M_w/M_n = 1.25). The deprotection of the trimethylsilyl group from the two block copolymers produced new block copolymers containing poly(secondary aminostyrene) block. Anionic reactivity of SBA and basic properties of PSBA are discussed in terms of the ¹³C chemical shift of β‐carbon in the vinyl group of SBA and steric effect. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2039–2048, 1999     

Preparation of high‐molecular‐weight poly(L‐lactic acid)‐based polymers through direct condensation polymerization in bulk state

Poly(L ‐lactic acid‐co‐succinic acid‐co‐1,4‐butanediol) (PLASB) was synthesized by a direct condensation copolymerization of L ‐lactic acid, succinic acid (SA), and 1,4‐butanediol (BD) in bulk state using titanium(IV) butoxide (TNBT) as a catalyst. Weight average molecular weight (M_w) of PLASB increased from 3.5 × 10⁴ to 2.1 × 10⁵ as the content of SA and BD went up from 0.01 to 0.5 mol/100 mol of L ‐lactic acid (LA). PLASB having M_w in the range from 1.8 × 10⁵ to 2.1 × 10⁵ showed tensile properties comparable to those of commercially available poly(L ‐lactic acid) (PLLA). In sharp contrast, homopolymerization of LA in bulk state produced PLLA with M_w as low as 4.1 × 10⁴, and it was too brittle to prepare specimens for the tensile tests. M_w of PLASB synthesized by using titanium(IV)‐2‐ethyl(hexoxide), indium acetate, indium hydroxide, antimony acetate, antimony trioxide, dibutyl tin oxide, and stannous‐2‐ethyl 1‐hexanoate was compared with that of PLASB obtained by TNBT. Ethylene glycol oligomers with different chain length were added to LA/SA in place of BD to investigate effect of chain length of ethylene glycol oligomers on the M_w of the resulting copolymers. Biodegradability of PLASB was analyzed by using the modified Sturm test. Toxicity of PLASB was evaluated by counting viable cell number of mouse fibroblast cells that had been in contact with PLASB discs. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 466–472, 2006     

Macromonomers by activated polymerization of oxiranes. Synthesis and polymerization

Macromonomers were obtained by cationic polymerization of propylene oxide and epichlorohydrin proceeding by the activated monomer mechanism with hydroxyethyl acrylate as initiator. Up to DP _n ～ 15 for propylene oxide and DP _n ～ 20 for epichlorohydrin, polymerization proceeds as a living process, giving with quantitative yields macromonomers with functionality equal to one, controlled molecular weight and narrow molecular weight distribution (M _wM _n<1.2) free of side products. In the higer molecular weight region, side reactions become increasingly noticeable. Propylene oxide macromonomers undergo radical homopolymerization. Homopolymerization of macromonomer with M _n = 8×10² gives graft copolymers with M _n up to 7.2×10³ in copolymerization with styrene, completely soluble graft copolymers with M _n ～ 2×10⁴ were obtained. Radical copolymerization of epichlorohydrin macromonomers with styrene gives initially soluble products with M _n ～ 6×10⁴ were obtained. Radical copolymerization of epichlorohydrin macromonomers with styrene gives initially soluble products with M_n～ 6×10⁴, which are converted in the later stages into insoluble gels, apparently due to the chain transfer to chloromethly groups of the polyepichlorohydrin chains.     

Coagulation rate studies of spinnable chitosan solutions

The coagulation properties of some mixtures of 5% chitosan in 2% aqueous acetic acid were investigated with the goal of determining the optimal coagulation conditions for the spinning of chitosan fibers. The chitosan was characterized and found to possess a deacetylation value of 84.9 ± 0.2%. Molecular weight of the chitosan was also measured; based on intrinsic viscosity, the M_v value was 7.73 × 10⁵ g mol⁻¹, and based on high-pressure liquid chromatography, the M_w value was 1.14 × 10⁵ g mol⁻¹. Solutions of 5% chitosan/2% acetic acid were prepared, filtered, and extruded through a large-diameter hole syringe into coagulation baths of varying composition that were all strongly basic in nature, at least a pH of 12 or greater. For each coagulant, time was varied from between 22 s and 2 minutes at room temperature. A second set of experiments was conducted where the temperature was varied from 20°C to 70°C at a constant time of 45 s. In a third set of experiments, using a 1M NaOH coagulant, different chitosans were also analyzed. Throughout all of the experiments, a distinct moving boundary between coagulated and uncoagulated polymer was observed within the cylindrical-shaped polymer fibers. Using a series of equations based on Fick's 2nd Law, a straight line relationship has been demonstrated between boundary motion and time and between boundary motion and temperature for each coagulant tested. The activation energy for each coagulant was also determined. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 117–127, 1997     

Polybenzimidazole (PBI) molecular weight and Mark‐Houwink equation

The molecular weight, and intrinsic viscosity of polybenzimidazole (PBI) and its phosphonylated derivatives are reported. The relationship between intrinsic viscosity [η] and weight average molecular weight (M_w) for PBI has been established in H₂SO₄ and DMF‐LiCl. The Mark Houwink constants K_w of 5.2 × 10^?3 mL/g, α of 0.92 for H₂SO₄ solvent systems and, K_w of 3.2 × 10^?2 mL/g, α of 0.754 for DMF‐LiCl solvent system have been determined at M_w < 65,000. The intrinsic viscosity of PBI determined by the Huggins–Kraemer method was compared with a single point method, and found that both methods fit well for PBI in relatively low concentration solvent system, giving ～ 99% accuracy. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis,characterization, and chelating properties of the polymacromonomer: Poly[(ethyleneglycol) methyl ether methacrylate]

The radical polymerization of the macromonomer poly(ethyleneglycol) methyl ether methacrylate with ammonium persulfate at 60°C was carried out. The polymer was completely soluble in water. Yield was 75%. The polymacromonomer was characterized by Fourier transform infrared, proton nuclear magnetic resonance (NMR), and ¹³C NMR spectroscopy. M_n, M_w, and the polydispersity were determined by gel permeation chromatography. The polymacromonomer showed a high thermal stability with a TDT_50% of 420°C. The metal ion binding capacity of this polychelatogen with respect to different metal ions was investigated through the liquid‐phase polymer‐based retention (LPR) technique. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2929–2934, 2002     

Molecular weights of natural rubbers from selected temperate zone plants

Molecular weights and molecular weight distributions are compared by gel permeation chromatography for rubbers from 33 north temperate zone plants, guayule, and Hevea. Rubbers isolated from all the northern plants had much lower weight-average molecular weight (M _w) values (9.72 × 10⁴–4.95 × 10⁵) than milled Hevea (1.31 × 10⁶) or guayule (1.28 × 10⁶) rubber. Pycnanthemum incanum, Lamiastrum galeobdolon, Monarda fistulosa, and Vernonia fasciculata produced potentially useful natural rubbers having M _w values above 4 × 10⁵ and polydispersity factors of 3.1–4.5.     

Self-aggregation and antibacterial activity of N-acylated chitosan

Chitosan was selectively N-acylated with acetic, propionic and hexanoic anhydrides under homogeneous condition to prepare N-acetyl chitosan (NACS), N-propionyl chitosan (NPCS) and N-hexanoyl chitosan (NHCS), respectively. NACSs with different N-acetylation degrees were obtained by controlling the degree of N-acetylation. The chemical structures of N-acylated chitosans including degree of deacetylation (DD), weight-average molecular weight (M_w), radius of gyration (〈S₂〉_Z^1/2) and crystal structure were studied by FTIR, GPC-LLS and X-ray diffraction techniques. Aggregation behavior of N-acylated chitosan was investigated by rheometer. Intramolecular aggregation of NPCS and NACS was stronger with NPCS stronger than NACS. The effect of concentration of polymer, concentration of salt and temperature on self-aggregation of NACS and NPCS was investigated. Hydrophobic interaction of N-acylated chitosan substituted with longer acyl chains was stronger. With moderate DD, intramolecular aggregation occurs predominantly. In vitro antibacterial activity test of N-acylated chitosans was evaluated against two Gram-positive bacteria and two Gram-negative bacteria. Relative inhibition time (RIT) of NHCS with concentration of 1 mg/ml against Escherichia coli and Pseudomonas aeruginosa was more than 2-6 times longer than that of NACS and NPCS. N-acylated chitosan with lower DD had inhibitory effect on the growth of bacteria than that with moderate DD. The results showed that intermolecular aggregation characteristic of N-acetylated chitosans with low DD may help in forming bridge to interact with bacterial cell.     

Preparation and properties of polyurethane/benzyl amylose semi‐interpenetrating networks

A series of semi‐interpenetrating polymer networks (semi‐IPNs) films were prepared from 20 wt % of benzyl amylose (BA) of different M_w and castor oil‐based polyurethane (PU) in N,N‐dimethylformamide (DMF). The weight‐average molecular weight (M_w), and radii of gyration (<S²>_z^1/2) of benzyl amylose were determined by laser scattering measurement, and the results suggested BA was in a compact coil conformation in DMF. Furthermore, the properties and miscibility of the polyurethane/benzyl amylose (PUBA) films were studied by scanning electronic microscopy, differential scanning calorimetry, dynamic mechanical thermal analysis, ultraviolet–visible spectrophotometer, and tensile testing. The PUBA films possessed much higher optical transmittance and tensile strength than the pure PU film regardless of the molecular weight of BA, but lower values of elongation at break were observed. With decreasing of the BA M_w from 9.24 × 10⁵ to 2.69 × 10⁵, interestingly, the elongation at break of the films increased from 135 to 326%. This might be ascribed to the decrease of crosslinking density of PU networks and the enhancement in freedom of the molecular motion. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010