Hydroxyl end-functionalized

Hydrolysis of 1 is carried out at room temperature by the slow addition of aqueous NH3 at 0°C (Scheme 2). The resulting hydroxyl end-functional polysiloxane (2) is dispersed as fine droplets in the aqueous medium and can be separated by centrifugation. When neat, 2 is a colorless fluid with molecular weight ranging from... 

A mixture consisting of hydroxyl end-functional polystyrene (25.80 g Mw 4000-5000 Da), 40 ml toluene, 1.37 ml mercaptoacetic acid, and 1 drop sulfuric acid were sparged with nitrogen for 30 minutes and then refluxed for 2 hours. The mixture was cooled in an ice bath and precipitated in methanol and the product isolated. 

A variety of block polymers, (A-B)jj, of variable "hard" and "soft" segments have been made (62. 63) by condensing rubbery a,o)-bis(dimethylamino)-polydimethylsiloxane (DMS) oligomers with hard oligomers containing bis-phenolic or hydroxyl end functions (Reaction 17) ... 

Aldehyde end-functionalized DEH-PPV 1 is obtained easily by Siegrist condensation with low polydispersity index (PDK1.3). It can be convert in hydroxyl end-functionalized PPV 2 after reduction of the aldehyde moiety. PPV 1 is converted into NMRP macro-initiator 3 by reacting the Grignard reagent of the appropriated alkoxyamine. ATRP macro-initiator 4 is obtained by a simple esterification on the hydroxyl end-functionalized PPV 2. 

Amphiphilic miktoarm stars of the typ>e ABC, where A is polyethylene (PE), B is polyethylenoxide (PEO), and C is poly(perfluoropropylene oxide), were also prepared via anionic polymerization, using arm in-out methodology " (Scheme 16). At the first step of the synthetic process, anioni-cally prepared PBd was temunated with a heterobifunctional proteaed agent. The resulting hydroxyl end-functionalized PBd was then hydrogenated to an end-functionalized polyethylene (PE) block, which served as a macroinitiator (Ml) for anionic... 

Give a schematic outline of the aforesaid synthesis of block copolymers and elaborate the four main steps (1) PIB synthesis (2) hydroxyl end-functionalization of PIB (3) formation of PIB-CTA and... 

Commercial end functional polymers have been converted to alkoxyamincs and used to prepare PKO-Worri-PS.040 The hydroxyl group of alkoxyamine 284 was used to initiate ring-opening polymerization of caprolactonc catalyzed by aluminum tris(isopropoxide) and the product subsequently was used to initiate S polymerization by NMP thus forming polycaprolactone-Wodr- P8.641 The alternate strategy of forming PS by NMP and using the hydroxyl chain end of the product to initiate polymerization of caprolactonc was also used. 

Di-hydroxyl end-capped PPG (18) is an intermediate in the formation of a common polyurethane prepolymer (20). End group functionality of this intermediate is important, as this hydroxyl functionality is modified to form the prepolymer. Any different end group structures could lead to the presence of prepolymer that will not form polyurethane of the desired structure. The desired reaction of the intermediate (18) to form the prepolymer (20) is described in Figure 21. Reaction of one unit of the intermediate (18) and two units of methylene diphenyl 4,4 -diisocyanate (MDI) results in the formation (nominally) of the prepolymer (20). 

A combination of NMR spectroscopy and MALDI-TOF MS is commonly employed in our laboratory for the characterisation of PPG polymers. Analysis of di-hydroxyl end-capped PPG (18) is initially described. The [H NMR spectrum [54] can be used to confirm the backbone structure of the polymer, as can be seen in Figure 22 (a and b are from the backbone of the polymer, with c from the methyl side chains). Peaks of low intensity, downfield of those from the backbone of the polymer, in the HNMR spectrum may be used to identify and quantify the allyl functionality in the polymer [55]. These resonances (d, e and f) are... 

Metallocene catalysis has been combined with ATRP for the synthesis of PE-fr-PMMA block copolymers [123]. PE end-functionalized with a primary hydroxyl group was prepared through the polymerization of ethylene in the presence of allyl alcohol and triethylaluminum using a zirconocene/MAO catalytic system. It has been proven that with this procedure the hydroxyl group can be selectively introduced into the PE chain end, due to the chain transfer by AlEt3, which occurs predominantly at the dormant end-... 

The bifunctional initiator 4-hydroxy-bulyl-2-bromoisobulyralc, HBBIB, promoted the ATRP of styrene as well as the cationic ring opening polymerization of THF [134], In the presence of Cu/CuBr2/PMDETA styrene was polymerized through the bromoisobutyrate function of HBBIB, to give PS chains end-functionalized with hydroxyl groups, PS-OH. The in situ... 

A combination of anionic and ATRP was employed for the synthesis of (PEO-b-PS) , n = 3, 4 star-block copolymers [148]. 2-Hydroxymethyl-l,3-propanediol was used as the initiator for the synthesis of the 3-arm PEO star. The hydroxyl functions were activated by diphenylmethyl potassium, DPMK in DMSO as the solvent. Only 20% of the stoichiometric quantity of DPMK was used to prevent a very fast polymerization of EO. Employing pentaerythritol as the multifunctional initiator a 4-arm PEO star was obtained. Well-defined products were provided in both cases. The hydroxyl end groups of the star polymers were activated with D PM K and reacted with an excess of 2-bromopropionylbro-mide at room temperature. Using these 2-bromopropionate-ended PEO stars in the presence of CuBr/bpy the ATRP of styrene was conducted in bulk at 100 °C, leading to the synthesis of the star-block copolymers with relatively narrow molecular weight distributions (Scheme 72). 

PS-b-PEO) , n = 3, 4 star-block copolymers were synthesized by ATRP and anionic polymerization techniques [149]. Three- or four-arm PS stars were prepared using tri- or tetrafunctional benzylbromide initiators in the presence of CuBr/bipy. The polymerization was conducted in bulk at 110 °C. The end bromine groups were reacted with ethanolamine in order to generate the PS stars with hydroxyl end groups. These functions were then activated by DPMK to promote the polymerization of ethylene oxide and afford the desired well-defined products (Scheme 73). 

Fig. 10. Complex dynamic viscosity as function of temperature for three different aliphatic hyperbranched polyesters based on bismethylol propionic acid and having different end-group structure - (O) propionate end-groups, ( ) benzoate end-groups, ( ) hydroxyl end-groups [118]...

Unfunctionalized, i.e., 2-hydroxypropylamide functional, hyperbranched polyesteramides have been tested in powder coating formulations together with stoichiometric (OH/COOH) amounts of acidic polyesters (Uralac). It was anticipated that the reaction of the hydroxyl end groups of the polyesteramide with the carboxylic acid end groups of the polyester would provide a well-crosslinked film with good mechanical properties by polymer/polymer cure. 

Recent advances in the development of well-defined homogeneous metallocene-type catalysts have facilitated mechanistic studies of the processes involved in initiation, propagation, and chain transfer reactions occurring in olefins coordi-native polyaddition. As a result, end-functional polyolefin chains have been made available [103].For instance, Waymouth et al.have reported about the formation of hydroxy-terminated poly(methylene-l,3-cyclopentane) (PMCP-OH) via selective chain transfer to the aluminum atoms of methylaluminoxane (MAO) in the cyclopolymerization of 1,5-hexadiene catalyzed by di(pentameth-ylcyclopentadienyl) zirconium dichloride (Scheme 37). Subsequent equimolar reaction of the hydroxyl extremity with AlEt3 afforded an aluminum alkoxide macroinitiator for the coordinative ROP of sCL and consecutively a novel po-ly(MCP-b-CL) block copolymer [104]. The diblock structure of the copolymer... 

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