Preparation and thermal characterization of block copolymers by macroazonitriles having glycidyl azide and epichlorohydrin moieties

Poly(glycidyl azide) (PGA) an energetic polymer and polyepichlorohydrin (PECH) were condensed with 4,4′ azobis(4-cyanopentanoyl chloride) (ACPC) to prepare macro-azo-initiators. Block copolymers containing each of these polyethers as a block segment combined with polystyrene (PS) or poly(vinyl acetate) (PVAc) have been drived by the polymerization of monomers initiated with this macro-azo-initiators. Thermal properties of block copolymers were investigated with differential scanning calorimetry (DSC) and thermogravimetry. DSC traces showed single glass transition temperatures in between the related segments of copolymers. Dynamic thermogravimetric analysis revealed the individual degradation behaviors of block segments © 1996 John Wiley & Sons, Inc.     

Styrene polymerization with a macroinitiator having siloxane units

Block copolymers containing segments of poly(dimethylsiloxane) (PDMS) and polystyrene were synthesized. Dihydroxy terminated PDMS M_n 2500 g/mol, was reacted with an ali-phatic diisocyanate (isophorone diisocyanate) and an aliphatic hydroperxide (t-butyl hy-droperoxide). The resulting polymeric peroxycarbamate having siloxane units (a new mac-roinitiator) was used as free radical initiator for vinyl polymerization of styrene. Formation of block copolymers was illustrated by several characterization methods such as chemical and spectroscopic analysis, fractionation, and GPC. Mechanical and thermal characterization of the copolymers were made by stress–strain tests and DSC. The surface properties and the morphology of the block copolymers were investigated by contact angle measurements and SEM. © 1996 John Wiley & Sons, Inc.     

Preparation of cellulose graft copolymers having polypeptide side chains and their blood compatibility

Blood compatibility of cellulose graft copolymers with poly(γ-benzyl-L -glutamate) and poly(N⁵-2-hydroxyethyl-L -glutamine) (Cell-g-PBLG and Cell-g-PHEG) was examined in vivo blood tests. For this purpose, Cell-g-PBLG graft copolymers with PBLG contents ranging from 7 to 60 mol % were prepared by polymerizing N-carboxy-γ-benzyl-L-glutamate(γ-BLG NCA) using aminoethyl cellulose (AE-Cell) with degree of substitution of 0.05 as macroinitiator. Graft copolymerization was carried out under a variety of conditions at 20°C in dimethyl-sulfoxide. Monomer conversion higher than 60% were obtained for all the polymerization runs. The solubility tests revealed that all of the AE-Cell and the polypeptides formed were grafted. The Cell-g-PHEG graft copolymers were prepared by treating Cell-g-PBLG graft copolymers with 2-amino-1-ethanol. Characterization of these graft copolymers were carried out by IR spectroscopy, DSC, and water content measurement. Tests for blood compatibility, in vivo, were made by a method of peripheral vein indwelling suture which was developed by one of the authors. The coating of graft copolymers on the polyester suture was made by casting either from formic acid solution of LiCl/dimethylacetamide solutions using water as the regenerating medium, and the polymer-coated sutures were implanted into a jugular and femoral vein of a dog. The results showed that the graft copolymers examined have excellent antithrombogenic properties.     

Physical properties of block copolymers of polydimethyl siloxane and polycarbonate

A detailed study of the physical properties of alternating block copolymers of polydimethyl siloxane and bisphenol-A polycarbonate is presented. The results suggest that the mechanical and optical properties of such materials are dependent upon the presence of associated regions as well as the nature of the chain between such regions. Dielectric, infrared, and DSC data as well as the stress and birefringence strain behavior are presented.     

Synthesis and characterization of poly(dimethyl siloxane) containing poly(vinyl pyrrolidinone) block copolymers

ABA‐type block copolymers containing segments of poly(dimethyl siloxane) and poly(vinyl pyrrolidinone) were synthesized. Dihydroxyl‐terminated poly(dimethyl siloxane) was reacted with isophorone diisocyanate and then with t‐butyl hydroperoxide to obtain macroinitiators having siloxane units. The peroxidic diradical macroinitiators were used to polymerize vinyl pyrrolidinone monomer to synthesize ABA‐type block copolymers. By use of physicochemical methods, the structure was confirmed, and its characterization was accomplished. Mechanical and thermal characterizations of copolymers were made by stress–strain tests and differential scanning calorimetric measurements. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1915–1922, 1999     

Preparation of block copolymers using a new polymeric peroxycarbamate

Block copolymers of poly(styrene-b-methyl methacrylate), poly(styrene-b-n-butyl methacrylate) and poly(methyl methacrylate-b-styrene) have been prepared via chemical reactions. A new polymeric peroxycarbamate is synthesized by reacting equimolar amounts of an aliphatic diisocyanate with a dihydroperoxide. This compound is an effective polymerization initiator, and is used to prepare active prepolymers containing fragments of polymeric peroxycarbamate. A second vinyl monomer is then incorporated to produce various block copolymers. Styrene contents, intrinsic viscosities and chemical and mechanical properties of the copolymers were determined.     

硅烷芳炔-硅氧烷芳炔嵌段共聚物的合成与表征

合成了不同链段长度的卤代硅氧烷,并用其与间二乙炔基苯格氏试剂反应,合成了两种硅烷芳炔-硅氧烷芳炔嵌段共聚物（SiO-b-PSA）,并制成碳纤维增强树脂复合材料。利用红外光谱（FT-IR）、核磁共振氢谱（¹H NMR）、凝胶渗透色谱（GPC）、旋转流变、差示扫描量热分析（DSC）、热失重分析（TGA）和悬梁臂冲击实验对共聚物及其复合材料的结构和性能进行表征。研究结果表明所合成的共聚物具有优良的耐热性和韧性,硅烷芳炔-硅氧烷芳炔嵌段共聚物在氮气气氛下的T_d5高于513℃,1000℃残留率高于78.9%,硅烷芳炔-硅氧烷芳炔嵌段共聚物/碳纤维复合材料的冲击强度高达（30.92±0.44） kJ·m^-2。     

Structural characterization and thermal behaviour of block copolymers of polydimethylsiloxane and polyamide having trichlorogermyl pendant groups

Block copolymers having a pendant trichlorogermyl group as a part of polyamide segment? (CO? R′? CO? NH? Ar? NH? )_xCO? R′? CO? and polydimethylsiloxane of general formula [(? CO? R′? CO? HN? Ar? NH)_x? CO? R′? CO? NH(CH₂)₃SiO(CH₃)₂ ((CH₃)₂SiO)_ySi(CH₃)₂(CH₂)₃ NH? ]_n (where R′ = CH₂CH(GeCl₃), CH(CH₃)CH(GeCl₃), CH(GeCl₃)CH(CH₃); Ar = C₆H₄, (? C₆H₃? CH₃)₂, (? C₆H₃? OCH₃)₂, 2,5‐(CH₃)₂? C₆H₂, C₆H₄? O? C₆H₄) were prepared by a polycondensation reaction and characterized using CHN and Ge analysis, Fourier transform infrared (FTIR) and ¹H NMR spectroscopy, thermogravimetric analysis (TGA) and molecular weight determination. They have a lamellar structure with weight‐average molecular weight in the range 1.21 × 10⁵–4.79 × 10⁵ g mol^?1. These copolymers display two glass transition temperatures and have an average decomposition temperature of 489 °C. TGA, FTIR and gas chromatography/mass spectrometry studies indicate that degradation of these block copolymers results in carbon monoxide, oligomeric siloxanes and polyamide fragments. They are thermally stable due to the hydrogen bonded interlinked chains of polyamide, while they absorb water due to the presence of Ge? Cl bonding. Copyright © 2010 Society of Chemical Industry     

Synthesis and properties of poly(imide siloxane) block copolymers with different block lengths

Several poly(imide siloxane) block copolymers with the same bis(γ‐aminopropyl)polydimethylsiloxane (APPS) content were prepared. The polyimide hard block was composed of 4,4′‐oxydianiline and 3,3′,4,4′‐diphenylthioether dianhydride (TDPA), and the polysiloxane soft block was composed of APPS and TDPA. The length of polysiloxane soft block increased simultaneously with increasing the length of polyimide hard block. For better understanding the structure–property relations, the corresponding randomly segmented poly(imide siloxane) copolymer was also prepared. These copolymers were characterized by FT‐IR, ¹H‐NMR, dynamic mechanical thermal analysis, thermogravimetric analysis, polarized optical microscope, rheology and tensile test. Two glass transition temperatures (T_g) were found in the randomly segmented copolymer, while three T_gs were found in the block copolymers. In addition, the T_gs, storage modulus, tensile modulus, solubility, elastic recovery, surface morphology and complex viscosity of the copolymers varied regularly with increasing the lengths of both blocks. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Mechanical properties of polysiloxanes: 1. Poly(tetramethyl-p-silphenylene siloxane) homopolymer and tetramethyl-p-silphenylene siloxane/dimethyl siloxane block copolymers

The mechanical behaviour of poly(tetramethyl-p-silphenylene siloxane) [poly(TMPS)] homopolymer and random block copolymers of tetramethyl-p-silphenylene siloxane-dimethyl siloxane [poly(TMPS-DMS)] of mean DMS block of 12 monomer units have been investigated over a wide range of composition and temperature using a Rheovibron viscoelastometer. The compositions ranged from TMPS/DMS wt % ratio of $\text{100}\text{0}$ to $\text{30}\text{70}$. The temperature intervals spanned from just above ?120°C to the point where melting became evident as dictated by the molecular architecture of each system. Two amorphous relaxation transitions, corresponding to DMS and TMPS phases, were found for copolymers with high TMPS content (?80 wt %). At lower TMPS compositions (?50 wt %) these transitions merge together. All dynamic transitions are a function of composition and crystallinity. The ‘hard’ TMPS phase provides crosslinks and acts as filler for the rubbery amorphous phase. The percentage elongation under tensile loading increases with the DMS amorphous content, which parallels an increase in clarity and decrease in density and crystallinity. A morphological model which depends on composition is proposed for these polysiloxanes. The model advanced is consistent with other physical evidence derived from other techniques. Changes in mechanical behaviour parallel changes in specimen morphology.     

Synthesis and characterization of silicon-containing graft copolymers

Poly(4-t-butoxycarbonyloxystyrene)-g-poly(dimethylsiloxane) and poly(t-butylmethacrylate)-g-poly(dimethylsiloxane) with various chemical compositions were synthesized via free radical polymerization of 4-t-butoxycarbonyloxystyrene (TBCS) or t-butylmethacrylate (TBMA) with silicone macromers. These macromers were prepared by anionic ring-opening polymerization of hexamethylcyclotrisiloxane (D₃) and subsequent termination with a chlorosilane compound having a methacrylate functionality. The morphology of the graft copolymer systems was investigated by DSC and TEM.     

Preparation,characterization, and properties of cellulose–polyacrylamide graft copolymers

Graft copolymers of acrylamide on cellulose materials (α‐cellulose 55.8%, DP 287.3) obtained from Terminalia superba wood meal and its carboxymethylated derivative (DS 0.438) were prepared using a ceric ion initiator and batch polymerization and modified batch polymerization processes. The extent of graft polymer formation was measured in graft level, grafting efficiency, molecular weight of grafted polymer chains, frequency of grafting as a function of the polymerization medium, and initiator and monomer concentrations. It was found that the modified batch polymerization process yielded greater graft polymer formation and that graft copolymerization in aqueous alcohol medium resulted in enhanced levels of grafting and formation of many short grafted polymer chains. Viscosity measurements in aqueous solutions of carboxymethyl cellulose‐g‐polyacrylamide copolymer samples showed that interpositioning of polyacrylamide chains markedly increased the specific viscosity and resistance to biodegradation of the graft copolymers. The flocculation characteristics of the graft copolymers were determined with kaolin suspension. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 913–923, 2003     

Blending of polystyrene with styrene-siloxane block and graft copolymers

A preliminary study on the efficiency of styrene-siloxane block and graft copolymer as toughening additives for polystyrene has been made. Block and graft copolymers of required molecular weight were synthesized for making compatible blends with polystyrene. Compatibility of these systems was evaluated through differential scanning calorimetry, thermo-mechanical analysis, rheovibron studies, and scanning electron microscopy. A good miscibility of block and graft copolymers was confirmed by these methods. Higher work of rupture in these blended polystyrene samples further demonstrates the feasibility of styrene-siloxane block and graft copolymers as good toughening material for a brittle polystyrene matrix. The mechanical properties have been related to the morphology and the amount of siloxane content in the blended polystyrene.     

Morphology and mechanical properties of poly(dimethyl siloxane-b-styrene-b-dimethyl siloxane) block copolymers

The films of poly(dimethyl siloxane-b-styrene-b-dimethyl siloxane) block copolymers cast from different solvents showed significant changes in both the phase morphology and the tensile behaviour. Methyl ethyl ketone and tetrahydrofuran gave hard films and appear to have a continuous polystyrene phase. Conversely cyclohexane, a good solvent for polydimethyl siloxane segment gave softer more elastic films. Intrinsic viscosity data of block copolymers of varying siloxane content showed highest value in toluene and least in cyclohexane which is a theta solvent for polystyrene segment. The tensile properties are also influenced by thermal ageing of films at 100 and 150°C.     

Preparation and properties of graft and block copolymers of poly(p-phenylene terephthalamide) with polybutadiene

Graft copolymers of polybutadiene (PBD) onto poly(p-phenylene terephthalamide) (PPTA) were prepared by the nucleophilic substitution of N-metalated PPTA with telechelic PBD having bromide end groups. Block copolymers were synthesized by the condensation reaction of telechelic PBD having acid chloride end groups with amino-group-terminated PPTA. The structure of these copolymers was identified by IR spectra. Graft and block copolymers contained PBD segments up to 85 wt % and 45 wt %, respectively. Thermomechanical analyses (TMA) proved the existence of distinctive primary absorption peak corresponding with T_g of PBD for both graft and block copolymers. The T_g's of both types of the copolymers were further ascertained by the DSC curves. TMA curves suggested that the microphase separation occurred between PPTA and PBD. The incorporation of PPTA segments into PBD increased the decomposition temperature compared with the blend polymer composed of PPTA and PBD with the same composition.