serialize std::map using sstream

I'm working on serialising std::map using sstream in C++. Serialising function:

template <class key, class value>
std::string serializeMap(const std::map<key, value>& v){
    std::stringstream ss;
    std::for_each(v.begin(), v.end(), [&ss](const std::pair<key, value>& s){
            ss.write ((char*)&s, sizeof(std::pair<key,value>));
        });
    return ss.str();
}

And de-serialize using this:

template <class key, class value>
void deSerializeMap(const std::string& s, std::map<key, value>& v){

    std::stringstream ss1;

    ss1<<s;

    int pos = 0;
    printf("\nlen %d\n", s.size());
    while(ss1){
        char* ar = new char[sizeof(std::pair<key, value>)];
        ss1.read(ar, sizeof(std::pair<key, value>));
        v.insert(*(reinterpret_cast<std::pair<key, value>*>(ar)));
        pos+=sizeof(std::pair<key, value>);
        ss1.seekg(pos);
        delete[] ar;
    }

}

This works as expected using std::string. I had to use a C function that takes const char* as an argument, I tried using c_str() and adding a NULL character to the char array, but strlen gives zero. Is there something I'm missing?