Synthesis and hydrophilicity of poly(butylene 2,6‐naphthalate)/poly(ethylene glycol) copolymers

Poly(butylene 2,6‐naphthalate) (PBN)/poly(ethylene glycol) (PEG) copolymers were synthesized by the two‐step melt copolymerization process of dimethyl‐2,6‐naphthalenedicarboxylate (2,6‐NDC) with 1,4‐butanediol (BD) and PEG. The copolymers produced had different PEG molecular weights and contents. The structures, thermal properties, and hydrophilicities of these copolymers were studied by ¹H NMR, DSC, TGA, and by contact angle and moisture content measurements. In particular, the intrinsic viscosities of PBN/PEG copolymers increased with increasing PEG molecular weights, but the melting temperatures (T_m)_, the cold crystallization temperatures (T_cc)_, and the heat of fusion (ΔH_f) values of PBN/PEG copolymers decreased on increasing PEG contents or molecular weights. The thermal stabilities of the copolymers were unaffected by PEG content or molecular weight. Hydrophilicities as determined by contact angle and moisture content measurements were found to be significantly increased on increasing PEG contents and molecular weights. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2677–2683, 2006     

Lipase Catalyzed Synthesis and Thermal Properties of Poly(dimethylsiloxane)–Poly(ethylene glycol) Amphiphilic Block Copolymers

Resin immobilized lipase B from Candida antarctica (CALB) was used to catalyze the condensation polymerization of two difuctional siloxane and poly(ethylene glycol) systems. In the first system, 1,3-bis(3-carboxypropyl)tetramethyldisiloxane was reacted with poly(ethylene glycol) (PEG having a number-average molecular weight, M_n = 400, 1000 and 3400 g mol⁻¹, respectively). In the second system, α,ω-(dihydroxy alkyl) terminated poly(dimethylsiloxane) (HAT-PDMS, M_n = 2500 g mol⁻¹) was reacted with α,ω-(diacid) terminated poly(ethylene glycol) (PEG, M_n = 600 g mol⁻¹). All the reactions were carried out in the bulk (without use of solvent) at 80 °C and under reduced pressure (500 mmHg vacuum gauge). The progress of the polyesterification reactions was monitored by analyzing the samples collected at various time intervals using FTIR and GPC. The thermal properties of the copolymers were characterized by DSC and TGA. In particular, the effect of the chain length of the PEG block on the molar mass build up and on the thermal stability of the copolymers was also studied. The thermal stability of the enzymatically synthesized copolymers was found to increase with increased dimethylsiloxane content in the copolymers.     

Dewetting and microphase separation in symmetric polystyrene‐block‐polyisoprene diblock copolymer ultrathin films

The kinetics of surface structure evolution in ultrathin films of low‐molecular‐weight polystyrene‐block‐polyisoprene (M_w: 7300 g mol^?1–7300 g mol^?1) diblock copolymer at temperatures below the bulk order‐to‐disorder transition temperature are presented. Films with two different thicknesses were studied as a function of annealing temperature using atomic force microscopy. These film thicknesses enabled the investigation of the competition between microphase separation and dewetting that resulted in two different morphologies: long‐range bicontinuous structures and random holes. Three distinctive stages of structure evolution were observed in bicontinuous structure, with the underlying mechanism compared with spinodal dewetting. Thicker films presented holes on their surfaces upon annealing at elevated temperatures, and kinetics of formation of the holes were discussed. We found that the molecular mobility determined the rates of dewetting, while the microphase separation hardly affected the dewetting process. © 2015 Society of Chemical Industry     

Synthesis and characterization of poly(ethylene‐co‐trimethylene terephthalate)s

Taking advantage of a melt polycondensation process, a series of copolyesters composed of pure terephthalate acid (PTA), ethylene glycol (EG), and 1,3‐propanediol (1,3‐PDO) were synthesized. The component, molecular weight, molecular weight distribution, and thermal properties of the copolymers were characterized. The results show that the contents of trimethylene terephthalate (TT) units in the resulting copolyesters are higher than PDO compositions in original diol. Oligomer content in the copolyesters varies with the compositions and attains a minimum value when the TT ingredient is 49.52 mol %. The glass transition temperature (T_g) of the copolyesters varies from 78.5°C for PET (polyethylene terephthalate) to 43.5°C for PTT (polytrimethylene terephthalate) and decreases monotonically with the components. The copolyesters are amorphous copolymers when TT content is in the range of 32.4–40.8 mol %, as calculated from the melting enthalpy (ΔH_m) measured via differential scanning calorimetry. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1511–1521 2006     

Synthesis and characterization of the biomaterial poly(lactic acid‐co‐Nε‐carbobenzoyloxy‐L‐lysine) via direct melt copolymerization

With D,L ‐lactic acid and N^ϵ‐carbobenzoyloxy‐L ‐lysine [Lys(Z)] as the starting monomer material and tin dichloride as the catalyst, the drug carrier material poly(lactic acid‐co‐N^ϵ‐carbobenzoyloxy‐L ‐lysine) was synthesized via direct melt polycondensation. The copolymer was systematically characterized with intrinsic viscosity testing, Fourier transform infrared spectroscopy, ¹H‐NMR, gel permeation chromatography, differential scanning calorimetry, and X‐ray diffraction. The influences of different feed molar ratios were examined. With increasing molar feed content of Lys(Z), the intrinsic viscosity, weight‐average molecular weight, and polydispersity index (weight‐average molecular weight/number‐average molecular weight) gradually decreased. Because of the introduction of Lys(Z) with a big aromatic ring into the copolymer, the glass‐transition temperature gradually increased with increasing feed charge of Lys(Z), and all of the copolymers were amorphous. The copolymers, with weight‐average molecular weights from 10,500 to 6900 Da, were obtained and could reach the molecular weight level of poly(lactic acid) modified by Lys(Z) via the ring‐opening polymerization of the cyclic intermediates, such as lactide and morpholine‐2,5‐dione. However, a few terminal carboxyl groups might have been deprotected during the polymerization reaction under high temperatures. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Improving the antifouling properties of polypropylene surfaces by melt blending with polyethylene glycol diblock copolymers

Protein‐resistant polyethylene‐block‐poly(ethylene glycol) (PE‐b‐PEG) copolymers of different molecular weights at various concentrations were compounded by melt blending with polypropylene (PP) polymers in order to enhance their antifouling properties. Phase separation of the PE‐b‐PEG copolymer and its migration to the surface of the PP blend, was confirmed by attenuated total reflectance–Fourier transform infrared, X‐ray photoelectron spectroscopy, and static water contact angle measurements. Enrichment of PEG chains at the surface of the blends increased with increasing PE‐b‐PEG copolymer concentration and molecular weight. The PP blends compounded with PE‐b‐PEG copolymer having the lowest molecular weight (875 g mol^?1), at the lowest concentration (1 wt %), gave the lowest bovine serum protein adsorption (30% less) compared to that of neat PP. At higher concentrations (5 and 10 wt %), and higher molecular weights (920, 1400, and 2250 g mol^?1), the PE‐b‐PEG copolymers leached‐out resulting in protein adsorption comparable to that of neat PP. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46122.     

Rheological and mechanical properties of poly (ethylene acrylic acid) and low density polyethylene blends

Rheological properties of poly (ethylene‐acrylic acid) (PEA) and low density poly ethylene (LDPE) blends having varied amounts of LDPE from 0 to 100% have been evaluated at different temperatures (115, 120, and 130°C) and shear rates (61.33–613.30 s^?1) using a Monsanto processability tester. A reduction in the melt viscosity of the PEA/LDPE blends was noticed with increasing the shear rate. The observed positive deviation in the experimental melt viscosities of the blends is an indication of the synergy present in the blends during melt processing. The activation energy (E_a) of flow calculated using Arrhenius relation for PEA, LDPE, and their respective blends lies in the range 29.98–40.56 kJ mol^?1. The experimental activation energy of flow of the blends was higher than that obtained from the additivity rule. Highest activation energy was noticed for the blends containing 60–80% by weight of LDPE in PEA/LDPE blends, which is an indication for the miscibility of the blends at these ratios. The physicomechanical properties such as density, tensile behavior, tear strength, and hardness (Shore A) of PEA, LDPE, and their blends have been evaluated as a function of varying amounts of LDPE. The obtained physicomechanical properties of the PEA/LDPE blends lie in between that of pure polymers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A unifying approach for melt rheology of linear polystyrene

Several studies of melt rheological properties of polystyrene have been conducted over the past 50 years. Several approaches, including empirical models, have been developed to understand the behavior of materials using simple equations. The existing melt rheology models are best suited for high‐molecular‐weight polymers whose T_g does not vary. In this work, a semiempirical viscosity equation has been derived, including the effect of T_g dependence on molecular weight, to describe the melt rheology of low‐molecular‐weight polymers. The equation is derived based on a combination of well‐known concepts, such as the effects of free volume and molecular dynamics on polymer rheology. This provides a better understanding of the rheological behavior in the low‐molecular‐weight regime with respect to temperature and molecular weight. Because of the industrial trend towards lower molecular weight materials for applications such as high solids coatings, this unifying approach, based on the free volume theory with a simple expression, is of extreme practical significance. This equation can predict the zero shear viscosity behavior for different molecular weights, including low‐molecular‐weight regions, and temperatures. Viscosity calculations using the empirical equation agree with published experimental data. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2597–2607, 2007     

Synthesis and properties of polystyrene‐b‐poly(ethylene oxide)‐b‐polystyrene triblock copolymers

A series of well‐defined and property‐controlled polystyrene (PS)‐b‐poly(ethylene oxide) (PEO)‐b‐polystyrene (PS) triblock copolymers were synthesized by atom‐transfer radical polymerization, using 2‐bromo‐propionate‐end‐group PEO 2000 as macroinitiatators. The structure of triblock copolymers was confirmed by ¹H‐NMR and GPC. The relationship between some properties and molecular weight of copolymers was studied. It was found that glass‐transition temperature (T_g) of copolymers gradually rose and crystallinity of copolymers regularly dropped when molecular weight of copolymers increased. The copolymers showed to be amphiphilic. Stable emulsions could form in water layer of copolymer–toluene–water system and the emulsifying abilities of copolymers slightly decreased when molecular weight of copolymers increased. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 727–730, 2006     

Stereocomplex crystallization and spherulite growth behavior of poly(l-lactide)-b-poly(d-lactide) stereodiblock copolymers

The non-isothermally and isothermally crystallized stereodiblock copolymers of poly(l-lactide) (PLLA) and poly(d-lactide) (PDLA) with equimolar l-lactyl and d-lactyl units and different number-average molecular weights (M_n) of 3.9 × 10³, 9.3 × 10³, and 1.1 × 10⁴ g mol⁻¹, which are abbreviated as PLLA-b-PDLA copolymers, contained only stereocomplex crystallites as crystalline species, causing higher melting temperatures of the PLLA-b-PDLA copolymers compared to those of PLLA homopolymers. In the case of non-isothermal crystallization, the cold crystallization temperatures of the PLLA-b-PDLA copolymers during heating and cooling were respectively lower and higher than those of PLLA homopolymers, indicating accelerated crystallization of PLLA-b-PDLA copolymers. In the case of isothermal crystallization, in the crystallizable temperature range, the crystallinity (X_c) values of the PLLA-b-PDLA copolymers were lower than those of the PLLA homopolymers, and were susceptible to the effect of crystallization temperature in contrast to that of homopolymers. The radial growth rate of the spherulites (G) of the PLLA-b-PDLA copolymers was the highest at the middle M_n of 9.3 × 10³ g mol⁻¹. This trend is different from that of the PLLA homopolymers where the G values increased monotonically with a decrease in M_n, but seems to be caused by the upper critical M_n values of PLLA and PDLA chains as in the case of PLLA/PDLA blends (in other papers), above which homo-crystallites are formed in addition to stereocomplex crystallites. The disturbed crystallization of PLLA-b-PDLA copolymers compared to that of the PLLA/PDLA blend is attributable to the segmental connection between the PLLA and PDLA chains, which interrupted the free movement of those chains of the PLLA-b-PDLA copolymers during crystallization. The crystallite growth mechanism of the PLLA-b-PDLA copolymers was different from that of the PLLA/PDLA blend.     

Stereocomplex formation between poly(L‐lactic acid) and poly(D‐lactic acid) with disproportionately low and high molecular weights from the melt

Poly(L ‐lactic acid) (PLLA) and poly(D ‐lactic acid) (PDLA) with very different weight‐average molecular weights (M_w) of 4.0 × 10³ and 7.0 × 10⁵ g mol^?1 (M_w(PDLA)/M_w(PLLA) = 175) were blended at different PDLA weight ratios (X_D = PDLA weight/blend weight) and their crystallization from the melt was investigated. The presence of low molecular weight PLLA facilitated the stereocomplexation and thereby lowered the cold crystallization temperature (T_cc) for non‐isothermal crystallization during heating and elevated the radial growth rate of spherulites (G) for isothermal crystallization, irrespective of X_D. The orientation of lamellae in the spherulites was higher for the neat PLLA, PDLA and an equimolar blend than for the non‐equimolar blends. It was found that the orientation of lamellae in the blends was maintained by the stereocomplex (SC) crystallites. Although the G values are expected to decrease with an increase in X_D or the content of high‐molecular‐weight PDLA with lower chain mobility compared with that of low‐molecular‐weight PLLA, G was highest at X_D = 0.5 where the maximum amount of SC crystallites was formed and the G values were very similar for X_D = 0.4 and X_D = 0.6 with the same enantiomeric excess. This means that the effect of SC crystallites overwhelmed that of chain mobility. The nucleating mechanisms of SC crystallites were identical for X_D = 0.1–0.5 in the T_c range 130–180 °C. Copyright © 2011 Society of Chemical Industry     

Melt rheological behavior of a triblock copolymer based on aramide end‐segments

Melt rheological behavior of a ABA triblock polymer made of poly(tetramethylene oxide) (PTMO) (M_n = 2,900 g mol^?1) soft segment and aramide hard segment was studied. The aramide end‐segments ( A ) were short and mono‐disperse in length. The mid‐segment ( B ) consisted of PTMO₂₉₀₀ extended with terephthalate units to a molecular weight of 9000 g mol^?1. The molecular weight of the triblock was 9700 g mol^?1. Rheological behavior of this material was studied by parallel‐plate and capillary method. The ABA triblock copolymer was compared with a B polymer (PTMO‐terephthalate) of a similar molecular weight. The low molecular weight B polymer had a Newtonian behavior. The low molecular weight triblock copolymer had at high frequencies a low complex viscosity. However, at low frequencies the triblock copolymer had a very high complex viscosity. Also the G″/G′ ratio decreased with decreasing frequency to values less then one and the G′ seemed to have at low frequencies a plateau value. The activation energy of the process increased in value with decreasing shear rate. All these results indicate that the triblock copolymer at low frequencies had a gel‐like behavior and this probably due to the clustering of the aramide segments. The aramide clusters are thought to be the (weak) network points of the gel. This network was also found to have a time dependant rheological response and thus a thixotropic behavior. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of poly(ethylene glycol) on the solid‐state polymerization of poly(ethylene terephthalate)

Poly(ethylene glycol) (PEG) and end‐capped poly(ethylene glycol) (poly(ethylene glycol) dimethyl ether (PEGDME)) of number average molecular weight 1000 g mol^?1 was melt blended with poly(ethylene terephthalate) (PET) oligomer. NMR, DSC and WAXS techniques characterized the structure and morphology of the blends. Both these samples show reduction in T_g and similar crystallization behavior. Solid‐state polymerization (SSP) was performed on these blend samples using Sb₂O₃ as catalyst under reduced pressure at temperatures below the melting point of the samples. Inherent viscosity data indicate that for the blend sample with PEG there is enhancement of SSP rate, while for the sample with PEGDME the SSP rate is suppressed. NMR data showed that PEG is incorporated into the PET chain, while PEGDME does not react with PET. Copyright © 2005 Society of Chemical Industry     

Microporous membranes of polyoxymethylene from a melt‐extrusion process: (I) effects of resin variables and extrusion conditions

A two‐part study utilizing polyoxymethylene (POM) was undertaken to investigate a three stage process (melt extrusion/annealing/uniaxial stretching) (MEAUS) employed to produce microporous films. In this first part, three POM resins (D, E, and F) were melt extruded into tubular films (blowup ratio; BUR = 1), where resin D has a higher weight average molecular weight (M_w) than resin E, but both possess similar and relatively narrow molecular‐weight distributions (MWD). In contrast, resin F is characterized by a distinctly broader MWD while its M_w is slightly higher than resin D. Specific attention was focused upon the morphological and crystal orientation results as a function MWD and M_w. A stacked lamellar morphology was obtained in each case from the melt extrusion; however, the type of stacked lamellar morphology, planar or twisted, and the orientation state was found to depend upon both the resin characteristics and the melt‐extrusion conditions. Atomic force microscopy and wide‐angle X‐ray scattering were the main techniques utilized to study the melt‐extruded films while dynamic melt rheometry in conjunction with the Carreau‐Yasuda model aided in differentiating the melt‐flow behavior of the three resins. Small‐angle light scattering (SALS) was also employed to characterize the morphological state. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2944–2963, 2001     

Synthesis and characterization of poly(ethylene isophthalate‐co‐ethylene terephthalate) copolyesters

Poly(ethylene isophthalate‐co‐ethylene terephthalate) (PEIPET) copolymers of various compositions and molecular weights were synthesized by melt polycondensation and characterized in terms of chemical structure and thermal and rheological properties. At room temperature, all copolymers were amorphous and thermally stable up to about 400°C. The main effect of copolymerization was a monotonic increase of glass transition temperature (T_g) as the content of ethylene terephthalate units increased. The Fox equation accurately describes the T_g–composition data. The presence of ethylene terephthalate units was found to influence rheological behavior in the melt, with the Newtonian viscosity increasing as the content of ethylene terephthalate units increased. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 186–193, 2004     

Preparation and biodegradation of copolyesters based on poly(ethylene terephthalate) and poly(ethylene glycol)/oligo(lactic acid) by transesterification

The poly(ethylene terephthalate‐co‐ethyleneoxide‐co‐DL ‐lactide) copolymers were successfully prepared by the melt reaction between poly(ethylene terephthalate), poly(ethylene glycol), and DL ‐oligo(lactic acid) without any catalysts. The transesterification between ethylene terephthalate, ethyleneoxide, and lactide segments during the reaction was confirmed by the ¹H NMR analysis. The effect of reaction temperatures and the starting feed ratios on the molecular microstructures, molecular weights, solubility, thermal properties, and degradability of the copolyesters was extensively studied. The values of crystallization temperature, melting temperature, crystallization, and melting enthalpy of the copolyesters were found to be influenced by the reaction temperatures, starting feed ratios, etc. The copolyesters showed good tensile properties and were found to degrade in the soil burial experiments during the period of 3 months. The morphology of the copolyester films were also investigated by scanning electron microscopy during soil burial degradation. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Characterization of poly(3,3-bisethoxymethyl oxetane) and poly(3,3-bisazidomethyl oxetane) and their block copolymers

The homopolymers, poly(3,3-bisethoxymethyl oxetane) (polyBEMO), poly(3,3-bisazidomethyl oxetane) (polyBAMO), and triblock copolymers based on these homopolymers and a statistical copolymer center block composed of BAMO and 3-azidomethyl-3-methyl oxetane AMMO were synthesized and characterized by differential scanning calorimetry, modulus-temperature, optical microscopy, membrane osmometry, and solution and melt viscosity. The values of K and a for the Mark-Houwink equation were found to be 7.29 × 10^?3 mL/g and 0.80, respectively, for polyBEMO at 25°C using number-average molecular weights. Glass transition temperatures were in the range ?25 to ?40°C and melting temperatures were between 65 and 90°C for all polymers. The melting temperature was found to increase as expected with molecular weight. Melt viscosities of triblock copolymers with polyBAMO end blocks were at least an order of magnitude lower than those with polyBEMO end blocks and clear optically, suggesting that the polyBAMO-based triblock copolymers formed one phase in the melt, while the polyBEMO-based triblock materials (milk white) phase separated. The addition of filler raised the melt viscosity to a level between that predicted by the Guth-Smallwood and the Mooney equations.     

Effects of molecular weight on dual light‐ and thermo‐responsive behaviors of homopolymers with azobenzene units and terminal oligo(ethylene glycol) units

A series of water‐soluble dual light‐ and thermo‐responsive homopolymers bearing azobenzene units and terminal oligo(ethylene glycol) units with well‐defined molecular weight (M _n = 0.69 × 10⁴ to 4.60 × 10⁴ g mol^?1) were synthesized via reversible addition–fragmentation chain transfer polymerization. All the homopolymers exhibited reversible photoisomerization and their lower critical solution temperatures showed an unusual increase with increasing molecular weight. Interestingly, by increasing the molecular weight, the aggregate morphology of these polymers was found to evolve from a spherical to a cylindrical shape. © 2017 Society of Chemical Industry     

PLA/chain‐extended PEG blends with improved ductility

Melt blending of polylactic acid (PLA) and a chain‐extended polyethylene glycol (CE‐PEG) have been performed in an effort to toughen the PLA without significant loss of modulus and ultimate tensile strength. The chain‐extended PEG was prepared with melt condensation of a low molecular weight PEG and 4,4′‐methylenebis(phenylisocyanate) (MDI) for enhancement of the molecular weight of PEG. The thermal and mechanical properties, miscibility and phase morphologies of blends were investigated. By using thermal and fracture surface analysis, the blends were found to be a partially miscible system with shifted glass transition temperatures. The addition of CE‐PEG leads to slight decrease in tensile strength and modulus, while the elongation at break is characterized by an important increase (540%), compared with neat PLA and PLA/PEG (low molecular weight PEG, M_n = 35,000). The relative ductility of PLA/CE‐PEG is 40 times higher than that of neat PLA. The brittle fracture of neat PLA was transformed into a ductile fracture by the addition of CE‐PEG. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of Hydrophobicity of PEO–PPO–PEO Block Copolymers on Micellization and Solubilization of a Model Drug Nimesulide

The present work explored the molecular implications governing the solubilization of a model drug nimesulide (NIM) in micelles of ethylene oxide-propylene oxide (EO–PO) triblock copolymers. The aggregation behavior and solubilization studies on four copolymers each with the same mol mass of central PPO block equal to 2,250 and varying % PEO was examined by means of UV–VIS. Moreover, high-sensitivity differential scanning calorimetry, and Fourier transform infrared spectrometry measurements were used to evaluate the critical micellization temperature. The solubilization at different temperatures (30, 37, 45 °C), pH (2 to 10) and in the presence of added sodium chloride (0–2 M) was monitored and the partition coefficient (P) and the free energy of solubilization (ΔG _s^o) were calculated. The site of solubilization of NIM in micelles was also probed. The NIM solubility decreased with increases in the PEO molecular weight; the drug resides in the micelle core.