Preparation and properties of new random and block copolyamides derived from 1,3-bis(3-aminopropyl)tetramethyldisiloxane,aromatic diamines,and isophthaloyl chloride

Random and block disiloxane-containing copolyamides were prepared through one- and two-step procedures, respectively, by the low temperature solution polycondensation in chloroform containing triethylamine hydrochloride starting from 1,3-bis(3-aminopropyl)tetramethyldisiloxane, an aromatic diamine [3,4'-diaminodiphenyl ether (ODA) or m-phenylenediamine], and isophthaloyl chloride. The random copolyamides exhibited composition-dependent single glass transition temperature (T_g), and gave transparent and tough films by solution casting or hot pressing. The ODA-based block copolyamides had two T_g's, and the solvent-cast transparent films exhibited microphase separated morphology. The block copolymers gave better quality films than the single-phase random copolymers. © 1992 John Wiley & Sons, Inc.     

Preparation and properties of novel soluble aromatic polyimides from 4,4′-diaminotriphenylamine and aromatic tetracarboxylic dianhydrides

New aromatic polyimides containing triphenylamine unit were prepared by two different methods, i.e., a conventional two-step method starting from 4,4′-diaminotriphenylamine and aromatic tetracarboxylic dianhydrides and the one-step thioanhydride method starting from the aromatic diamine and aromatic tetracarboxylic dithioanhydrides. Both procedures yielded high-molecular-weight polyimides with inherent viscosities of 0.47–1.17 dL/g. Some of these polymers were soluble in organic solvents such as N,N-dimethylacetamide, N-methyl-2-pyrrolidone, m-cresol, and pyridine. All the polyimides afforded transparent, flexible, and tough films, and the color varied from pale yellow to dark red, depending markedly on the tetracarboxylic acid components. The glass transition temperatures (T_gs) of these polyimides were in the range of 287–331°C and the 10% weight loss temperatures were above 520°C in air. The polyimides prepared by the one-step method exhibited better solubility in organic solvents and had somewhat lower T_gs than the polymers prepared by a conventional two-step method.     

Novel aromatic poly(amide-hydrazide)s based on the bipyridine. Part I: Synthesis, characterization and thermal stability

A series of new poly(amide-hydrazide)s were obtained by the direct polycondensation of 5-amino 5′-carbohydrazido-2,2′-bipyridine with commercially available diacids by means of triphenyl phosphite and pyridine in the N-methyl-2-pyrrolidone (NMP) solutions containing dissolved LiCl. The resulting hydrazide containing polymers exhibited inherent viscosities in the 0.42-0.64 dL/g range. All copolymers were soluble in polar solvents such as NMP and dimethyl sulfoxide (DMSO). Most of the amorphous hydrazide copolymers formed flexible and tough films by solvent casting. The poly(amide-hydrazide)s had glass-transition temperatures (T_g) between 178 and 206 °C. All hydrazide copolymers could be thermally converted into the corresponding poly(amide-oxadiazole) approximately in the region of 300-400 °C, as evidenced by the DSC thermograms. The oxadiazole polymers and copolymers showed a dramatically decreased solubility and higher T_g when compared to their respective hydrazide prepolymers. They exhibited T_gs of 197-248 °C and were stable up to 450 °C in air or nitrogen.     

Synthesis and properties of bisphenol A–terphenol poly(arylene ether sulfone)–polydimethylsiloxane segmented block copolymers

We have synthesized new poly(arylene ether sulfone) (PAES) and polydimethylsiloxane (PDMS) segmented block copolymers where the PAES segments contain 20–30% of 4,4′-dihydroxyterphenol (DHTP) and 70–80% of bisphenol A (BA) units. The tensile and thermal properties of these new polymeric materials were measured and were compared to those of existing bisphenol A PAES–PDMS segmented block copolymers (BA PAES-b-PDMS). Also, a high molecular weight BA–DHTP PAES random copolymer containing 80% BA and 20% DHTP was prepared and its properties were compared to Udel®, a commercial PAES based on BA. The BA–DHTP PAES random copolymer had a significantly higher modulus, 1800 MPa and a higher T_g, 196 °C when compared to Udel®. In the segmented block copolymer materials, increased modulus and tensile strain at break (elongation) were also found when DHTP was incorporated into the PAES segments.     

Synthesis and characterization of new polyimides containing calix[4]arenes in the polymer backbone

Two diaminocalix[4]arene monomers were synthesized from p-tert-butylcalix[4]arene through a 4-step reaction sequence. New copoly(amic acid)s containing calix[4]arene moieties on the polymer backbone were successfully synthesized in N-methyl-2-pyrrolidone by polycondensations of 4,4′-oxydiphthalic anhydride (ODPA) with the diaminocalix[4]arene monomers using 4,4′-oxydiphenylene diamine (ODA) as a comonomer. These copoly(amic acid)s were soluble in aprotic polar solvents, so that they can be processed in various ways. The copoly(amic acid) precursors were thermally converted to the corresponding copolyimides in films. The copolyimide films are amorphous, but insoluble in common solvents. They are thermally stable up to 366°C. The copolyimides exhibit relatively high TEC's, low T_g's, low refractive index, low dielectric constant, low optical anisotropy, low dielectric anisotropy, and low water uptake, compared to those of conventional ODPA-ODA polyimide. These property characteristics were interpreted in regard to bulky, cone-like calix[4]arene moieties and their effects on the chain conformation and morphological structure. The processability and property characteristics support that both of the copolyimides containing calix[4]arene moieties are potential candidate materials suitable for membranes, antioxidant additives, chemical sensor devices, and microelectronic devices. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2013–2026, 1999     

Synthesis and properties of new block copolymers based on poly(ether sulfone) and aramids

New poly(ether sulfone)–aramid block copolymers were synthesized from an α, ω-diamineterminated poly(ether sulfone) oligomer, aromatic diamines, and aromatic dicarboxylic acid chlorides by the low-temperature solution polycondensation in N-methyl-2-pyrrolidone. By the introduction of aramid into the poly(ether sulfone), the glass transition temperatures of the block copolymers rose and the mechanical properties were significantly improved. Microphase separation, which often takes place in many block copolymers, did not occur in the present block copolymers. © 1993 John Wiley & Sons, Inc.     

Synthesis and characterization of aromatic polythiazole-amides from new aromatic diamines containing phenyl-pendant thiazole units

New aromatic diamines containing phenyl-pendant thiazole units were synthesized in three steps starting from p-nitrobenzyl phenyl ketone. Novel aromatic polyamides containing phenyl-pendant thiazole units were prepared by the low-temperature solution polyconden-sation of 1,4- (or 1.3-) bis[5-(p-aminophenyl)-4-phenyl-2-thiazolyl] benzene with various aromatic dicarboxylic acid chlorides in N,N-dimethylacetamide. High molecular weight polyamides having inherent viscosities of 0.5–3.0 dL/g were obtained quantitatively. The polythiazole-amides with m-phenylene, 4,4′-oxydiphenylene, and 4,4′-sulfonyldiphenylene units were soluble in N-methyl-2-pyrrolidone, N,N-dimethylacetamide, and pyridine, and gave transparent flexible films by casting from the solutions. These organic solvent-soluble polyamides displayed prominent glass transition temperatures (T_g) between 257 and 325°C. On the other hand, the polythiazole-amides with p-phenylene and 4,4′-biphenylene units were insoluble in most organic solvents, and had no observed T_g. All the polythiazole-amides started to decompose at about 400°C with 10% weight loss being recorded at 450–525°C in air. © 1995 John Wiley & Sons, Inc.     

Synthesis and properties of multiblock copolymers based on polydimethylsiloxane and polyamides from dicarboxylic acid and diisocyanate terminated functionalities

Polydimethylsiloxane (PDMS)–polyamide multiblock copolymers were successfully synthesized via diisocyanate route by two different procedures, i.e., the one-step and two-step methods, In the two-step method, α, ω-diisocyanate-terminated polyamide oligomers, which were prepared in situ from a mixture of isophthalic acid (IPA) and azelaic acid (AZA) with 4,4′-methylenedi (phenyl isocyanate) (MDI) in 1,3-dimethyl-2-imidazolidone (DMI) in the presence of 3-methyl-1-phenyl-2-phosopholene 1-oxide catalyst, were reacted with α, ω-bis (10-carboxydecyl) polydimethylsiloxane (PDMS-diacid) leading to the formation of multiblock copolymers. In the one-step method, the reaction components, MDI, IPA, AZA, and PDMS-diacid were reacted all together in DMI in the presence of the catalyst. These polymerizations gave multiblock copolymers having inherent viscosities in the range of 0.36–1.12 dL/g in N,N-dimethylacetamide (DMAc). These multiblock copolymers were soluble in amide-type solvents, and transparent (or translucent) and ductile films could be cast from the solutions in a mixture of DMAc and bis(2-ethoxyethyl) ether. The multiblock copolymers prepared by the two-step method had better-defined, microphase-separated morphology than those obtained by the one-step method. The mechanical properties of PDMS–polyamide multiblock copolymer films were found to be highly dependent on the PDMS content; the tensile strength and modulus of the films decreased with increasing the PDMS content.     

Phenylquinoxaline–Aryl ester block copolymers

Phenylquinoxaline–aryl ester block copolymers were synthesized using well-defined phenolic hydroxyl terminated oligomers via a monomers/oligomer approach. Phenylquinoxaline oligomers with molecular weights of 5600 and 12,900 g/mol were prepared from the condensation of 1,4-bis(phenylglyoxalyl)benzene and 3,3′-diaminobenzidine in the presence of 4-hydroxylbenzil. The oligomers were copolymerized with isophthaloyl chloride and bisphenol A in tetrachloroethane to afford the desired phenylquinoxaline–aryl ester block copolymers. Copolymers with polyester compositions ranging from 15–50 wt % were prepared by controlling the monomers/oligomer stoichiometry. The majority of the materials displayed single phase morphologies with T_gs intermediate to the T_gs for the poly (phenylquinoxaline) and polyester homopolymers. Plots of the reciprocal of the T_g of the copolymers versus composition agreed well with values predicted by the Fox equation. A multiphase morphology was obtained for the copolymer with the highest polyester block length (? 13,000 g/mol), which displayed a T_g at 190 and 300°C indicative of a glassy–glassy system. Significant improvement in the elongations were observed for the copolymers relative to the poly(phenylquinoxaline) homopolymer. The improved elongations were obtained with minimal sacrifice to the modulus. These materials represent the first example of poly(phenylquinoxaline) block copolymers from well-defined phenylquinoxaline oligomers.     

Novel aromatic polyhydrazides and poly(amide-hydrazide)s based on “multiring” flexible dicarboxylic acids

Two flexible dicarboxylic acid monomers, 4,4′-[isopropylidenebis(1,4-phenylene)dioxy]dibenzoic acid ( 1 ) and 4,4′-[hexafluoroisopropylidenebis(1,4-phenylene)-dioxy]dibenzoic acid ( 3 ), were synthesized from readily available compounds in two steps in high yields. High molecular-weight polyhydrazides and poly(amide-hydra-zide)s were directly prepared from dicarboxylic acids 1 and 3 with terephthalic dihydrazide ( 5 ), isophthalic dihydrazide ( 6 ), and p-aminobenzhydrazide ( 7 ) by the phosphorylation reaction by means of diphenyl phosphite (DPP) and pyridine in N-methyl-2-pyrrolidone (NMP)/LiCl, or prepared from the diacyl chlorides of 1 and 3 with the hydrazide monomers 5–7 by the low-temperature solution polycondensation in NMP/LiCl. Less favorable results were obtained when using triphenyl phosphite (TPP) instead of DPP in the direct polycondensation reactions. Except for those derived from terephthalic dihydrazide, the resulting polyhydrazides and poly(amide-hydrazide)s could be cast into colorless, flexible, and tough films with good tensile strengths. All the hydrazide polymers and copolymers are amorphous in nature and are readily soluble in various polar solvents such as NMP and dimethyl sulfoxide (DMSO). Their T_gs were recorded in the range of 162–198°C and could be thermally cyclodehydrated into the corresponding polyoxadiazoles and poly(amide-oxadiazole)s approximately in the region of 300–380°C, as evidenced by the DSC thermograms. The oxadiazole polymers and copolymers showed a dramatically decreased solubility and higher T_g when compared to their respective hydrazide prepolymers. They exhibited T_gs of 190–216°C and were stable up to 450°C in air or nitrogen. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1847–1854, 1998     

Synthesis and characterization of new aromatic polyesters and polyethers derived from 1,2-bis(4-hydroxyphenyl)-1,2-diphenylethylene

New polyarylates and aromatic polyethers were synthesized from 1,2-bis(4-hydroxyphenyl)-1,2-diphenylethylene, and aromatic dicarboxylic acid chlorides and aromatic dihalides, respectively. The polyarylates having inherent viscosities of 0.28–1.05 dL/g were synthesized by either the two-phase method or the high-temperature solution method. All the polymers were easily soluble in N-methyl-2-pyrrolidone, N,N-dimethylformamide, pyridine, m-cresol, 1,4-dioxane, and 1,1,2,2-tetrachloroethane. They have glass transition temperatures in the range of 217–250°C and showed no weight loss below 315°C in both air and nitrogen atmospheres. Aromatic polyethers with inherent viscosities of 0.85–1.21 dL/g were obtained by the polycondensation of 1,2-bis(4-hydroxyphenyl)-1,2-diphenylethylene and aromatic difluorides in the presence of potassium carbonate. These polymers having glass transion temperatures of 193–220°C were also soluble in the aforementioned solvents and stable up to around 350deg;C in both atmospheres. © 1994 John Wiley & Sons, Inc.     

Structure analysis of a soluble polysiloxane-block-polyimide and kinetic analysis of the solution imidization of the relevant polyamic acid

A series of polysiloxane-block-polyimides were synthesized by solution imidization of the polyamic acids derived from the combination of 3,3′,4,4′-diphenylsulfonetetracarboxylic dianhydride (DSDA), 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), and diamino(polysiloxane) (PSX (M_w = 750)) in N-methyl-2-pyrrolidone (NMP). Their structures were analyzed by ¹H-, ¹³C-, and ²⁹Si-NMR spectra as well as by IR spectroscopy. The solid-state NMR spectrum was also measured to determine the spin–lattice relaxation time of the copolyimides. The observed relaxation times of both aromatic and polysiloxane segments were similar in the copolyimides having 10–30 wt % of PSX, while those in the copolyimide with 50 wt % of PSX was significantly different. This may be attributed to the morphology change due to the increase in PSX composition in the polymer backbone. The reduced viscosity of the copolyimides could be controlled by changing the monomer ratio in the feed or by adding an end-capping reagent such as phthalic anhydride into the polymerization system. The kinetic study of the solution imidization revealed that the imidization reaction obeyed second-order kinetics. The activation energy calculated for this imidization was 99.2 kJ/mol, being similar to that for the imidization of the DSDA-based aromatic polyimides. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2237–2245, 1998     

Synthesis of amphiphilic multiblock and triblock copolymers of polydimethylsiloxane and poly(N,N‐dimethylacrylamide)

The synthesis and spectroscopic characterization of a new family of amphiphilic multiblock and triblock copolymers is described. The synthetic methodology rests on the preparation of telechelic multifunctional and difunctional chain transfer agents easily available in two synthetic steps from commercially available polydimethylsiloxane‐containing starting materials. Telechelic polymers thus synthesized are used as macromolecular chain transfer agents in the reversible addition fragmentation chain transfer (RAFT) polymerization of N,N‐dimethylacrylamide (DMA) enabling the synthesis of (AB)_n‐type multiblock and ABA‐type triblock copolymers of varying compositions possessing monomodal molecular weight distribution. (AB)_n multiblock copolymers [(PDMA‐b‐PDMS)_n] were prepared with between 52 and 95 wt % poly(dimethylacrylamide) with number average molecular weights (M_n) between 14,000 and 86,000 (polydispersities of 1.20–2.30). On the other hand, ABA block copolymers with DMA led to amphiphilic block copolymers (PDMA‐b‐PDMS‐b‐PDMA) with M_n values between 9000 and 44,000 (polydispersities of 1.24–1.62). © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7033–7048, 2008     

Synthesis and Properties of Polyamides and Polyimides Derived From Diamines Having 2-Phenyl-4,5-Oxazolediyl Units and Polyamide/Montmorillonite Composite

Aromatic polyamides were synthesized from 4,5-bis(4-aminophenyl)-2-phenyloxazole (APO) or 4,5-bis[4(4-aminophenoxy)phenyl]-2-phenyloxazole (APPO) containing 2-phenyl-4,5-oxazolediyl units with several aromatic carboxylic dichlorides by a low-temperature solution polycondensation method. The polyamides were obtained quantitatively, and their inherent viscosities ranged from 0.48 to 1.25 dL g^?1. The glass transition temperatures (T _gs) were displayed between 234 to 311°C, and the residual weight at 600°C (Res.wt₆₀₀) exceeded 52% in nitrogen atmosphere. The polyamides showed good solubility in several aprotic polar solvents, such as N,N-dimethylacetoamide (DMAc), N-methyl-2-pyrrolidone (NMP), and dimethyl sulfoxide (DMSO). Aromatic polyimides were derived from APO or APPO with aromatic carboxylic dianhydrides through polyamic acids. The inherent viscosities of the polyamic acids, which were 0.53 to 1.02 dL g^?1, T _gs of the polyimides were observed between 259 to 361°C and their Res.wts₆₀₀ were above 70%. The polyamides and polyimides were amorphous and afforded thin, flexible and tough films. We also prepared a nanocomposite of the polyamide derived from APPO with organophilic montmorillonite clay.     

Synthesis and characterization of poly(p-arylene sulfide ketone/Schiff base) copolymers

Poly(p-arylene sulfide ketone/Schiff base) copolymers(PASK/SB) were prepared by solution polycondensation of 4,4’-diflurobenzophenone(DFBP) and N-phenyl(4,4’-diflurodiphenyl) ketimine(DFBI) with sodium sulfide in the presence of sodium hydroxide under normal pressure.Elemental analyses,FT-IR,NMR,DSC,TGA and XRD were used to characterize the resultant copolymers.It was found that the copolymers had good thermal properties with glass transition temperature(T_g) of 155.0-172.0°C,melting temperature(T_m) of 298-344°C,5%weight loss temperatures(T_d) of 471.0-501.5°C.These copolymers were almost amorphous with the content of DFBI beyond 30%.The polymer with 100% DFBI had excellent solubility,and it could dissolve in some solvents such as tetrahydrofuran(THF) and N-methyl-2- pyrrolidone(NMP).The processability of polymers was improved.Meantime the viscosity of PASK made from hydrolysis of PASK/SB(H-PASK/SB) was greatly improved from 0.135 dL/g to 0.605 dL/g.     

Novel triblock siloxane copolymers: Synthesis,characterization, and their use as surface modifying additives

Synthesis of novel triblock, polycaprolactone-b-polydimethylsiloxane (PDMS) and poly(2-ethyl-oxazoline)-b-PDMS copolymers were demonstrated. These materials were obtained via the ring-opening polymerization of ?-caprolactone or 2-ethyl-2-oxazoline monomers by using organofunctionally terminated PDMS oligomers as initiators and comonomers. Segment molecular weights in these copolymers were varied over a wide range between 1000 and 2000 g/mol and the formation of copolymers with desired backbone compositions were monitored by ¹H-NMR spectroscopy and GPC. DSC and TMA studies showed the formation of two phase morphologies with PDMS (T_g, ?120°C) and polycaprolactone (T_m, 50–60°C) or poly(2-ethyl-2-oxazoline) (T_g, 40-60°C) transitions respectively. The use of polycaprolactone-b-PDMS copolymers as surface modifying additives in polymer blends were also investigated. When these copolymers were blended at low levels (0.25–10.0% by weight) with various commercial resins such as, polyurethanes, PVC, PMMA, and PET, the resulting systems displayed silicone-like, hydrophobic surface properties, as determined by critical surface tension measurements or water contact angles. The effect of siloxane content, block length, base polymer type and morphology on the resulting surfaces are discussed.     

Preparation and characterization of organosoluble copolyimides based on a pair of commercial aromatic dianhydride and one aromatic diamine, 1,2-bis(4-aminophenoxy)-4-tert-butylbenzene, series

 A series of copolyimides with high molecular weights, excellent mechanical properties, heat-resistant properties, and good solubilities in organic solvents were synthesized from six kinds of commercial dianhydrides and 1,2-bis(4-aminophenoxy)-4-tert-butylbenzene. Monomers for synthesizing insoluble polyimides and monomers for synthesizing soluble polyimides were used to synthesize semialternating copolyimides with arbitrary solubilities. Fifteen kinds of soluble copolyimides were synthesized through chemical or thermal cyclodehydration. These copolyimides were found to be easily soluble as well as able to be processed by casting from solutions such as N-methyl-2- pyrrolidone, N,N-dimethylacetamide, dimethylformamide, dimethyl sulfoxide, m-cresol, and tetrahydrofuran. The easily dissolved characteristics of this series of copolyimides stemmed from the tert-butyl group, the ortho-linked aromatic unit, and the ether group within 4-tert-butylbenzene. Besides, when the dianhydride molecules used contained organosoluble groups and were mixed at varying molar ratios, the solubilities in organic solvents could be greatly enhanced. The copolyimides could improve the processability of polymers, while maintaining or increasing their excellent mechanical properties and heat-resistant properties. Received: 21 July 2000 Accepted: 13 December 2000     

Synthesis and properties of new poly(ether sulfone)amides

High molecular-weight aromatic polyamides were obtained from 1,5- and 2,6-bis-(4′-carboxy-4-phenylenoxy-sulfonyl)naphthalene by direct polycondensation reaction in N-methyl-2-pyrrolidone with various aromatic diamines, using triphenyl phosphite and pyridine as condensing agents. The polymers were characterized by elemental analysis, thermogravimetric analysis, differential scanning calorimetry, and infrared analysis. The polyamides, obtained in quantitative yield, possessed inherent viscosities in the range 0.42–1.70 dL/g, glass transition temperatures between 245–310°C, and 10% weight loss temperatures in nitrogen and air above 435 and 424°C, respectively. Most of the polymers were soluble in aprotic solvents. The effect of the structure on properties, such as solubility, T_g, and thermal behavior, were also studied. © 1996 John Wiley & Sons, Inc.     

Polyimides from 1,5-bis(4-amino-2-trifluoromethylphenoxy)naphthalene and aromatic tetracarboxylic dianhydrides

A new trifluoromethylated bis(ether amine), 1,5-bis(4-amino-2-trifluoromethylphenoxy)naphthalene, was synthesized in two steps starting from 1,5-dihydroxynaphthalene and 2-chloro-5-nitrobenzotrifluoride via nucleophilic aromatic substitution and catalytic reduction. A series of novel fluorinated polyimides with moderate to high molecular weights were synthesized from the diamine with various aromatic tetracarboxylic dianhydrides using a conventional two-stage process. All polyimides could afford flexible and tough films and most of them were soluble in strong polar solvents such as N-methyl-2-pyrrolidone (NMP) and N,N-dimethylacetamide (DMAc). The polyimides showed glass-transition temperatures (T_g) in the range of 253-315 °C (by DSC) and softening temperatures (T_s) in the range of 250-300 °C (by TMA). Decomposition temperatures for 5% weight loss all occurred above 500 °C in both air and nitrogen atmospheres. The dielectric constants of these polymers ranged from 3.17 to 3.64 at 1 MHz. The properties of these fluorinated polyimides were also compared with those of polyimides prepared from 1,5-bis(4-aminophenoxy)naphthalene with the same dianhydrides.     

Breadth of glass transition temperature in styrene/acrylic acid block,random, and gradient copolymers: Unusual sequence distribution effects

Block, random, and gradient copolymers of styrene (S) and acrylic acid (AA) are synthesized by conventional or controlled radical polymerization, and their glass transition temperature (T_g) behaviors are compared. The location and breadth of the T_gs are determined using derivatives of differential scanning calorimetry heating curves. Each S/AA random copolymer exhibits one narrow T_g, consistent with a single phase of limited compositional nanoheterogeneity. Block copolymers exhibit two narrow T_gs originating from nanophase separation into ordered domains with nearly pure S or nearly pure AA repeat units. Each gradient copolymer exhibits a T_g response with a ～50–56 °C breadth that extends beyond the upper T_g of the block copolymers. For copolymers of similar composition, the maximum value in the gradient copolymer T_g response is consistent with that of a random copolymer, which has an enhanced T_g relative to poly(acrylic acid) due to more effective hydrogen bonding when AA units are separated along the chain backbone by S units. These results indicate that gradient copolymers with ordered nanostructures can be rationally designed, which exhibit broad glass transitions that extend to higher temperature than the T_gs observed with block copolymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2842–2849, 2007