Polyether diols block copolymers

The polyether diols, block copolymers of PO-EO with terminal poly[EO] block are obtained absolutely identically to the previously described EO capped polyether triols, the difference being that the propoxylated intermediate is a propoxylated polyether diol. 

The work reported here is concerned with the syntheses and properties of polyether-ester block copolymers containing poly (tetramethylene ether) units of molecular weight of approximately 1000 as the amorphous polyether blocks and a variety of esters as the crystallizable hard segments. The purpose of this study is to correlate changes in synthesis and properties of these thermoplastic and elastomeric copolymers with changes in the concentration and nature of the ester segments, particularly the types of diol and diacid. 

Figure 1. Synthesis and structure of polyether-ester block copolymers (D — hydrocarbon portion of diol Ar = aromatic portion of the ester x,y = the number of repeat units in the respective ester and polyether-ester blocks)...

Elastomeric polyether-ester block copolymers were prepared by melt transesterification of poly(tetramethylene ether) glycol of molecular weight approximately 1000 with a variety of diols and esters. The ease of synthesis and the properties of these thermoplastic copolymers have been related to the chemical structure and concentration of the ester hard segments. 

As an example, a group of polyether diols (block PO-EO copolymers with terminal poly[EO] block) are the polyethers derived from propylene glycol (or DPG), PO and EO of MW of 2000 daltons and around 15-20% EO as a terminal block (Figure 4.29). 

Thomas et al. [1986] studied the effect of gamma irradiation (1,10,100 and 500 kGy) on PVC/TPE = 100 0, 75 25, 50 50, 25 75 and 0 100 blends (Table 11.9). As TPE a thermoplastic, elastomeric polyether-ester block copolymer of 1,4-butane-diol-polybutylene and glycol-terephthalic acid copolymer (ElytreF ), was used. The blends were prepared in an internal cam-type mixer at 80 rpm, 180°C, mixing time 7 min. TPE was added first,... 

Polyurethane-based FTPEs are produced by reacting fluorinated polyether diols with aromatic disocyanates. The resulting block copolymers contain fluorinated polyether soft segments.68 Another possible method of preparation of fluorinated TPE is dynamic vulcanization. Examples are a blend of a perfluoroplastic and a perfluoroelastomer containing curing sites or a combination of VDF-based fluo-roelastomers and thermoplastics, such as polyamides, polybutylene terephtalate, and polyphenylene sulhde.69 70... 

T inear polyurethane block copolymers have been objects of considerable -L/ research interest over recent years. These materials are composed of three parts, a diisocyanate, a low molecular weight chain extender (usually a diol but sometimes a diamine), and a low molecular weight rubbery polymer, frequently a polyether or polyester. The soft segment consists of the rubbery polymer while the diisocyanate and the chain extender form the hard segment These materials are classified as thermo-... 

Polyurethane-based FTPEs are produced by reacting fluorinated polyether diols with aromatic diisocyanates. The resulting block copolymers contain fluorinated... 

Most glycols or polyols such as polyether or hydrocarbon diols may be used in the reaction to give block copolymers. Other types of polyols such as polyester polyols may be used in the reaction to yield useful resins, but these will not give block copolymers. The multiple ester linkages in polyester act as multiple transfer sites so that a random copolymer is obtained. 

By using two oxiranic monomers, such as PO and EO, it is possible to obtain a great variety of polyether polyols homopolymers of PO, block copolymers PO-EO (with terminal or internal poly[EO] block) or random copolymers (heteropolyethers) of PO-EO, diols or triols of different MW. 

Table 4.14 Characteristics of polyether diols, bloc terminal poly[EO] block, with a MW ol k copolymer PO-EO, with 2000 daltons...

Chemistry Polyurethane is produced by the reaction of a polyol with an diisocyanate (or in some instances a polyisocyanate) in the presence of catalysts. The polyols of choice are poly(propylene glycol), block copolymers of ethylene oxide (10-15%) with propylene oxide, or the newer polymer polyols (based on polymers such as polystyrene or styrene-acrylonitrile copolymer). Polyester diols such as polycaprolactone diol can be used in place of the polyether polyol in this reaction. The isocyanate of choice is a mixture of the 2,4 and 2,6 isomers of tolylene di-isocyanate in the ratio of 80 20, generally referred to as 80 20TDI. Other isocyanates such as diphenylmethane di-isocyanate (MDI), hexamethylene di-isocyanate (HMDI), and isophorone di-isocyanate (IPDI) are also used. A tin-based or amine catalyst is used to promote the reaction. Given the wide choice of reactants available, the reaction can yield foams with a range of different mechanical and thermal characteristics. 

Common SS include polyethers, polyesters and polyalkyl glycols with glass transition temperatures in the range of -70°to -30°C. Commonly used macrodiols in the PUs synthesis are polyalkyl-diols, such as polyisobutylene diol [70], polybutadiene (PBU) [20, 71], or oligo-butadiene diols [72] as well as hydrogenated polybutadiene diol [20] polyether diols polytetrahydrofuran (PTHF or PTMO) [50-52], polyethylene glycol (PEG) or (PEO) [73], polypropyleneoxide (PPO) [73] or mixed blocks of them PEO-PPO-PEO [74] and PPO-THF [54] polyester diols poly(ethylene adipate) (PEA) [4,20], poly(butylene adipate) (PBA) [20, 73], and latterly polycaprolactone diol (PCL or PCD) [75], polyalkylcarbonate polyol [20] or mixed blocks of them, for example poly(carbonate-co-ester)diol [76], poly(hexamethylene-carbonate)diol [77], as well as poly(hexamethylene-carbonate-co-caprolactone)diol [78] and a mixed block copolymer of polyether and polyester blocks PCL-b-PTHF-b-PCL [79]. Examples schemes of macrodiols are shown in Eig. 1.9. 

A carboxyl-terminated unsaturated polyester was esterified with poly(oxy-ethylene) diols [70]. Using poly(oxyethylene) diol with a munber average molecular weight of 2000, partly crystalline block copolymers were obtained. The unsaturated block copolyether ester contained predominantly one terminal polyether group per molecule. Block unsaturated copolyetheresters with shorter poly(oxyethylene) terminal groups of M = 350 and 550 were also obtained. The effect of the composition of those UPRs on the mechanical and thermal properties was investigated [70]. The block copolyetherester with Mn = 2000 can be dissolved in styrene monomer, thus forming a UPR with acceptable viscosity at as little as 20% styrene. 

Segmented polyurethanes (PUs) are typical representatives of linear block copolymers of the type (A-B)jj and an important class of thermoplastic elastomers. They are composed of short alternating blocks of soft (SS) and hard segments (HS). The SS impart elastomeric character to the copolymer, whereas the HS form a solid phase (HS microdomains) through intermolecular association and impart dimensional stability to the array of macromolecules. Low molecular mass polyethers and polyesters are typically used as SS, while HS normally consist of an aromatic diisocyanate that has been chain extended with a low molecular weight diol or diamine to form an oligomeric aromatic urethane or urethane urea segment [1-3]. 

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